drm/omap: work-around for omap3 display enable

Seems that on omap3 enabling a crtc without any planes causes a sync
lost flood. This only happens on the first enable, and after that it
works. This looks like an HW issue and it's unclear why this is
happening or how to fix it.

This started happening after 897145d0


("drm/omapdrm: Move commit_modeset_enables() before commit_planes()")
which, as a work-around, changed omapdrm first to do the modeset enable,
and plane set only after that. This WA should be fine on all DSS
versions, but apparently OMAP3 DSS is an exception.

This patch reverts that work-around for OMAP3 DSS.

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