split out fbdev parts to prepare for drm/kms

The fbdev specifics are moved into fbmode_display to keep things
cleaner.

Signed-off-by: Rob Clark <robdclark@gmail.com>
drm/kms support

Add drmmode_display with the drm/kms support.

Signed-off-by: Rob Clark <robdclark@gmail.com>
dri2: page-flip support

Add swap/flip support and triple buffer.

Signed-off-by: Rob Clark <robdclark@gmail.com>