drm: omapdrm: Remove remap argument to omap_gem_get_paddr()

The function is always called with the remap argument set to true.
Hardcode that behaviour and remove it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>