Revert "drm: omapdrm: Let the DRM core skip plane commit on inactive CRTCs"

This reverts commit dadf4659.

If planes are not disabled when the they are not on any crtc anymore
they will remain active and may show as "ghosts" when the crtc they
were last on is active again.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>