support 32 bpp pixmaps when 24 bpp fb is used.
support 32 bpp pixmaps when 24 bpp fb is used.

Fixes background corruption in ubuntu.

Signed-off-by: Maarten Lankhorst <743c2818a341d71b99ed2b566f9f80c2fc288f93@canonical.com>

wzyy2/xf86-video-modesetting,patjak/xf86-video-gma500,patjak/xf86-video-gma500,wzyy2/xf86-video-modesetting