video: Moving mx3fb.c to CONFIG_VIDEO

mx3fb.c was based on CONFIG_LCD and is moved by this patch to
CONFIG_VIDEO, which has greater freedom in selecting videomodes
even at runtime.

This renders the accumulating list of display defines
(CONFIG_DISPLAY_VBEST..., CONFIG_DISPLAY_C057...) obsolete as
these may be setup through env variables:

uboot> setenv mydisplay 'video=ctfb:x:240,y:320,depth:16,mode:0,pclk:185925,
	le:9,ri:17,up:7,lo:10,hs:1,vs:1,sync:100663296,vmode:0'
uboot> setenv videomode ${mydisplay}

This commit also fixes the board config files for qong and
imx31_phycore boards as needed. The videomode settings of
previously supported displays are added to CONFIG_EXTRA_ENV_SETTINGS
now. CONFIG_SYS_MALLOC_LEN for imx31_phycore board is increased
to make the frame buffer allocation working with the changed
driver.

Signed-off-by: Helmut Raiger <helmut.raiger@hale.at>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Stefano Babic <sbabic@denx.de>