drm/rockchip: Constify function pointer structs

Moves a bunch of junk to .rodata from .data.

 drivers/gpu/drm/rockchip/dw_hdmi-rockchip.ko:
-.rodata                      772
+.rodata                      828
-.data                        148
+.data                         92

 drivers/gpu/drm/rockchip/rockchipdrm.ko:
-.rodata                      748
+.rodata                      760
-.data                        448
+.data                        436

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1450178476-26284-25-git-send-email-boris.brezillon@free-electrons.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
index b8ac5911..621f25c 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
@@ -66,7 +66,7 @@
 				     rockchip_fb->obj[0], handle);
 }
 
-static struct drm_framebuffer_funcs rockchip_drm_fb_funcs = {
+static const struct drm_framebuffer_funcs rockchip_drm_fb_funcs = {
 	.destroy	= rockchip_drm_fb_destroy,
 	.create_handle	= rockchip_drm_fb_create_handle,
 };