drm/gma500/psb: Use identical generic crtc funcs

This patch makes psb use the gma_xxx counterparts that are identical. I
took them in one sweep as they should not cause any regressions.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>

diff --cc drivers/gpu/drm/gma500/psb_intel_display.c
Simple merge