imx: mx6sabresd: fix splash logo drawing

After mxc_ipuv3 DM_VIDEO conversion showing splash image
doesn't work. Fix this. Also enable white on black console
configuration as it used to be with cfb_console driver.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Reported-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Fabio Estevam <festevam@gmail.com>