video: ipuv3: Set max display bpp to 32

The IPUv3 can handle 1920x1080x32bpp displays , set the max preallocated
framebuffer BPP to 32 to cater for all eventualities.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Anatolij Gustschin <agust@denx.de>