drm/cma: Update DEFINE_DRM_GEM_CMA_FOPS to add get_unmapped_area

Missing field get_unmapped_area which is necessary with device without MMU

Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Link: http://patchwork.freedesktop.org/patch/msgid/1492164819-10513-2-git-send-email-yannick.fertre@st.com
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

include/drm/drm_gem_cma_helper.h

@@ -50,6 +50,7 @@ to_drm_gem_cma_obj(struct drm_gem_object *gem_obj)
 		.read		= drm_read,\
 		.llseek		= noop_llseek,\
 		.mmap		= drm_gem_cma_mmap,\
+		.get_unmapped_area	= drm_gem_cma_get_unmapped_area,\
 	}
 
 /* free GEM object */