ENGR00175084 IPU-FB: change dma memory alloc gfp flags to GFP_KERNEL

ENGR00175084 IPU-FB: change dma memory alloc gfp flags to GFP_KERNEL

We only needs the dma buffer, don't care if it is from DMA Zone on i.mx SOC.

To fix the following bug:
mxc_ipudev_test: page allocation failure: order:13, mode:0x1
[<80042e08>] (unwind_backtrace+0x0/0xfc) from [<800b4dd8>]
	(warn_alloc_failed+0x9c/0x118)
[<800b4dd8>] (warn_alloc_failed+0x9c/0x118) from [<800b5ac4>]
	(__alloc_pages_nodemask+0x494/0x6ec)
[<800b5ac4>] (__alloc_pages_nodemask+0x494/0x6ec) from [<80046154>]
	(__dma_alloc+0xd4/0x2fc)
[<80046154>] (__dma_alloc+0xd4/0x2fc) from [<800463a0>]
	(dma_alloc_writecombine+0x24/0x2c)
[<800463a0>] (dma_alloc_writecombine+0x24/0x2c) from [<8024be34>]
	(mxcfb_set_par+0x3e4/0x4c0)
[<8024be34>] (mxcfb_set_par+0x3e4/0x4c0) from [<80235f08>]
	(fb_set_var+0x168/0x2a4)
[<80235f08>] (fb_set_var+0x168/0x2a4) from [<802363f8>](do_fb_ioctl+0x3b4/0x5f0)
[<802363f8>] (do_fb_ioctl+0x3b4/0x5f0) from[<800f58d0>](do_vfs_ioctl+0x80/0x5e4)
[<800f58d0>] (do_vfs_ioctl+0x80/0x5e4) from [<800f5e6c>] (sys_ioctl+0x38/0x60)
[<800f5e6c>] (sys_ioctl+0x38/0x60) from [<8003d500>] (ret_fast_syscall+0x0/0x30)
mxc_sdc_fb mxc_sdc_fb.0: Unable to allocate framebuffer memory
detected fb_set_par error, error code: -12

Signed-off-by: Wayne Zou <b36644@freescale.com>