ENGR00224700 IPUv3 FB:Support RGB24/RGB32/ABGR32 pixel formats

ENGR00224700 IPUv3 FB:Support RGB24/RGB32/ABGR32 pixel formats

Users may call FBIOPUT_VSCREENINFO framebuffer ioctrl to set
a framebuffer's pixel format by specifying bits_per_pixel field
and red/green/blue/transp fields of struct fb_var_screeninfo.
Users may also know a framebuffer's pixel format at which it is
working by calling FBIOGET_VSCREENINFO framebuffer ioctrl, red/
green/blue/transp bitfields of struct fb_var_screeninfo tell the
exact offset and length of each color component in a pixel. This
patch supports RGB24/RGB32/ABGR32 pixel formats with these 2 ioctrls.
To change the default pixel format when initializeing a framebuffer
at the first time, users may add 'fbpix=' option in framebuffer
kernel command line option, for example, 'video=mxcfb0:fbpix=ABGR32'
makes fb0's default pixel format be ABGR32. 'bpp=' option cannot
overwrite 'fbpix=' option, for example, 'video=mxfb0:fbpix=RGB24,
bpp=16' still makes fb0 work at RGB24 by default. To be back
compatible, this patch doesn't change the default pixel formats
(BGR24/BGR32/RGB565) for each bits_per_pixel, if users don't
provide valid 'fbpix=' option.

Signed-off-by: Liu Ying <Ying.Liu@freescale.com>