ENGR00229473 elcdif fb: fix lcd framebuffer potential recursive locking

ENGR00229473 elcdif fb: fix lcd framebuffer potential recursive locking

This can be detected by enabling CONFIG_LOCKDEP and CONFIG_PROVE_LOCKING
The dump log:

=============================================
[ INFO: possible recursive locking detected ]
3.0.35-02140-gb4181ce-dirty #959
---------------------------------------------
swapper/1 is trying to acquire lock:
 ((fb_notifier_list).rwsem){.+.+.+}, at: [<80088758>] __blocking_notifier_call_chain+0x44/0x88

 but task is already holding lock:
  ((fb_notifier_list).rwsem){.+.+.+}, at: [<80088758>] __blocking_notifier_call_chain+0x44/0x88

  other info that might help us debug this:
   Possible unsafe locking scenario:

CPU0
----
 lock((fb_notifier_list).rwsem);
 lock((fb_notifier_list).rwsem);

*** DEADLOCK ***

May be due to missing lock nesting notation

5 locks held by swapper/1:
 #0:  (&__lockdep_no_validate__){+.+.+.}, at: [<8027f244>] __driver_attach+0x48/0x98
 #1:  (&__lockdep_no_validate__){+.+.+.}, at: [<8027f254>] __driver_attach+0x58/0x98
 #2:  (registration_lock){+.+.+.}, at: [<8023a17c>] register_framebuffer+0x18/0x24c
 #3:  (&fb_info->lock){+.+.+.}, at: [<80238dc8>] lock_fb_info+0x18/0x3c
 #4:  ((fb_notifier_list).rwsem){.+.+.+}, at: [<80088758>] __blocking_notifier_call_chain+0x44/0x88

stack backtrace:
[<800405c4>] (unwind_backtrace+0x0/0xf8) from [<80097c78>] (__lock_acquire+0x1644/0x1c18)
[<80097c78>] (__lock_acquire+0x1644/0x1c18) from [<80098748>] (lock_acquire+0x84/0x98)
[<80098748>] (lock_acquire+0x84/0x98) from [<804d0aa8>] (down_read+0x34/0x44)
[<804d0aa8>] (down_read+0x34/0x44) from [<80088758>] (__blocking_notifier_call_chain+0x44/0x88)
[<80088758>] (__blocking_notifier_call_chain+0x44/0x88) from [<800887b4>] (blocking_notifier_call_chain+0x18/0x20)
[<800887b4>] (blocking_notifier_call_chain+0x18/0x20) from [<802397e0>] (fb_set_var+0x264/0x290)
[<802397e0>] (fb_set_var+0x264/0x290) from [<8024a320>] (lcd_init_fb+0x54/0x70)
[<8024a320>] (lcd_init_fb+0x54/0x70) from [<8024a3f0>] (lcd_fb_event+0x44/0xb4)
[<8024a3f0>] (lcd_fb_event+0x44/0xb4) from [<80088514>] (notifier_call_chain.isra.1+0x74/0xd0)
[<80088514>] (notifier_call_chain.isra.1+0x74/0xd0) from [<80088774>] (__blocking_notifier_call_chain+0x60/0x88)
[<80088774>] (__blocking_notifier_call_chain+0x60/0x88) from [<800887b4>] (blocking_notifier_call_chain+0x18/0x20)
[<800887b4>] (blocking_notifier_call_chain+0x18/0x20) from [<8023a2d4>] (register_framebuffer+0x170/0x24c)
[<8023a2d4>] (register_framebuffer+0x170/0x24c) from [<8024fe8c>] (mxc_elcdif_fb_probe+0x464/0x564)
[<8024fe8c>] (mxc_elcdif_fb_probe+0x464/0x564) from [<8028031c>] (platform_drv_probe+0x18/0x1c)
[<8028031c>] (platform_drv_probe+0x18/0x1c) from [<8027f0f0>] (driver_probe_device+0x90/0x19c)
[<8027f0f0>] (driver_probe_device+0x90/0x19c) from [<8027f290>] (__driver_attach+0x94/0x98)
[<8027f290>] (__driver_attach+0x94/0x98) from [<8027e2e4>] (bus_for_each_dev+0x5c/0x88)
[<8027e2e4>] (bus_for_each_dev+0x5c/0x88) from [<8027eabc>] (bus_add_driver+0x188/0x250)
[<8027eabc>] (bus_add_driver+0x188/0x250) from [<8027f750>] (driver_register+0x78/0x13c)
[<8027f750>] (driver_register+0x78/0x13c) from [<8001c838>] (mxc_elcdif_fb_init+0x38/0x48)
[<8001c838>] (mxc_elcdif_fb_init+0x38/0x48) from [<80035334>] (do_one_initcall+0x34/0x178)
[<80035334>] (do_one_initcall+0x34/0x178) from [<80008968>] (kernel_init+0x84/0x124)
[<80008968>] (kernel_init+0x84/0x124) from [<8003b614>] (kernel_thread_exit+0x0/0x8)

In fact, we don't need support dynamically switch the framebuffer.
so, we only need do once registeration in probe function.

Signed-off-by: Robby Cai <R63905@freescale.com>
Acked-by: Lily Zhang