drm: omapdrm: Prefix all plane functions with omap_plane_
drm: omapdrm: Prefix all plane functions with omap_plane_

This matches the rest of the file and clarifies the functions' purpose.

Signed-off-by: Laurent Pinchart <3ded2f39a78f0d7044839546f95841842b4d7c96@ideasonboard.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs