splash: fix logo drawing if CONFIG_VIDEO_LOGO enabled

After mxc_ipuv3 DM_VIDEO conversion board configs with enabled
CONFIG_VIDEO_LOGO do not show splash screen (previosly drawing
splash screen worked via cfb_console driver with CONFIG_VIDEO_LOGO
enabled). Use splash_source library for loading splash images
when CONFIG_SPLASH_SOURCE is selected, otherwise prepare built-in
video logo for drawing.

Signed-off-by: Anatolij Gustschin <agust@denx.de>