Fallback to 24 bit depth if 32 bit depth is not supported.
Fallback to 24 bit depth if 32 bit depth is not supported.

If the DRM does not support 32 bit depth at 32 bpp we fallback
to 24 bit depth at 32 bpp. The display controller will effectively
ignore the alpha channel.

Change-Id: Ia142aa50a1d22f6ff3d99e3b45f87273d9f6f953

mdrjr/xf86-video-armsoc,mdrjr/xf86-video-armsoc