video: mxsfb: remove fb_phys/fb_size from platform_data

There is no in-tree users of mxsfb_platform_data fb_phys/fb_size.
With CMA support in the kernel, there is no real need for platform to
reserve memory and pass address and size into driver via platform_data.
So let's remove fb_phys/fb_size from mxsfb_platform_data to ease full
device tree adoption.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>