drm/i2c/sil164: Constify function pointer structs

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

 drivers/gpu/drm/i2c/sil164.ko:
-.text                       1660
+.text                       1656
-.rodata                       56
+.rodata                      104
-.data                        212
+.data                        164
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/1450178476-26284-21-git-send-email-boris.brezillon@free-electrons.comSigned-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i2c/sil164_drv.c

@@ -341,7 +341,7 @@ sil164_encoder_destroy(struct drm_encoder *encoder)
 	drm_i2c_encoder_destroy(encoder);
 }
 
-static struct drm_encoder_slave_funcs sil164_encoder_funcs = {
+static const struct drm_encoder_slave_funcs sil164_encoder_funcs = {
 	.set_config = sil164_encoder_set_config,
 	.destroy = sil164_encoder_destroy,
 	.dpms = sil164_encoder_dpms,