usb: dwc3: dwc3-omap: Fix the crash on module removal

usb: dwc3: dwc3-omap: Fix the crash on module removal

Following crash is seen on dwc3_omap removal
Unable to handle kernel NULL pointer dereference at virtual address 00000018
pgd = ec098000
[00000018] *pgd=ad1f9831, *pte=00000000, *ppte=00000000
Internal error: Oops: 17 [#1] SMP ARM
Modules linked in: usb_f_ss_lb g_zero usb_f_acm u_serial usb_f_ecm u_ether libcomposite configfs snd_usb_audio snd_usbmidi_lib snd_rawmidi snd_hwdep snd_soc_omap snd_pcm_dmaengine snd_soc_core snd_compress snd_pcm snd_tim]
CPU: 0 PID: 1296 Comm: rmmod Tainted: G        W     3.15.0-rc4-02716-g95c4e18-dirty #10
task: ed05a080 ti: ec368000 task.ti: ec368000
PC is at release_resource+0x14/0x7c
LR is at release_resource+0x10/0x7c
pc : [<c0044724>]    lr : [<c0044720>]    psr: 60000013
sp : ec369ec0  ip : 60000013  fp : 00021008
r10: 00000000  r9 : ec368000  r8 : c000e7a4
r7 : 00000081  r6 : bf0062c0  r5 : ed7cd000  r4 : ed7d85c0
r3 : 00000000  r2 : 00000000  r1 : 00000011  r0 : c086d08c
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: 10c5387d  Table: ac098059  DAC: 00000015
Process rmmod (pid: 1296, stack limit = 0xec368248)
Stack: (0xec369ec0 to 0xec36a000)
9ec0: 00000000 00000001 ed7cd000 c034de94 ed7cd010 ed7cd000 00000000 c034e194
9ee0: 00000000 bf0062cc ed7cd010 c03490b0 ed154cc0 ed4c2570 ed2b8410 ed156810
ed156810 bf006d24 c034db9c c034db84 c034c518
9f20: bf006d24 ed156810 bf006d24 c034cd2c bf006d24 bf006d68 00000800 c034c340
9f40: 00000000 c00a9e5c 00000020 00000000 bf006d68 00000800 ec369f4c 33637764
9f60: 616d6f5f 00000070 00000001 ec368000 ed05a080 c000e670 00000001 c0084010
9f80: 00021088 00000800 00021088 00000081 80000010 0000e6f4 00021088 00000800
9fa0: 00021088 c000e5e0 00021088 00000800 000210b8 00000800 e04f6d00 e04f6d00
9fc0: 00021088 00000800 00021088 00000081 00000001 00000000 be91de08 00021008
9fe0: 4d768880 be91dbb4 b6fc5984 4d76888c 80000010 000210b8 00000000 00000000
[<c0044724>] (release_resource) from [<c034de94>] (platform_device_del+0x6c/0x9c)
[<c034de94>] (platform_device_del) from [<c034e194>] (platform_device_unregister+0xc/0x18)
[<c034e194>] (platform_device_unregister) from [<bf0062cc>] (dwc3_omap_remove_core+0xc/0x14 [dwc3_omap])
[<bf0062cc>] (dwc3_omap_remove_core [dwc3_omap]) from [<c03490b0>] (device_for_each_child+0x34/0x74)
[<c03490b0>] (device_for_each_child) from [<bf0062b4>] (dwc3_omap_remove+0x6c/0x78 [dwc3_omap])
[<bf0062b4>] (dwc3_omap_remove [dwc3_omap]) from [<c034db9c>] (platform_drv_remove+0x18/0x1c)
[<c034db9c>] (platform_drv_remove) from [<c034c518>] (__device_release_driver+0x70/0xc8)
[<c034c518>] (__device_release_driver) from [<c034cd2c>] (driver_detach+0xb4/0xb8)
[<c034cd2c>] (driver_detach) from [<c034c340>] (bus_remove_driver+0x4c/0x90)
[<c034c340>] (bus_remove_driver) from [<c00a9e5c>] (SyS_delete_module+0x10c/0x198)
[<c00a9e5c>] (SyS_delete_module) from [<c000e5e0>] (ret_fast_syscall+0x0/0x48)
Code: e1a04000 e59f0068 eb14505e e5943010 (e5932018)
---[ end trace 7e2a8746ff4fc811 ]---
Segmentation fault

[ balbi@ti.com : add CONFIG_OF dependency ]

Signed-off-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>