drm: omapdrm: Refactor CRTC creation code

Create a omap_modeset_create_crtc() function to avoid duplicating plane
and CRTC creation code.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

diff --cc drivers/gpu/drm/omapdrm/omap_drv.c
Simple merge

diff --cc drivers/gpu/drm/omapdrm/omap_plane.c
Simple merge