drm: Constify struct drm_fb_helper_funcs

There's no need for this to be modifiable. Make it const so that it can
be put into the .rodata section.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.c
index 5107fc4..7e706c4 100644
--- a/drivers/gpu/drm/msm/msm_fbdev.c
+++ b/drivers/gpu/drm/msm/msm_fbdev.c
@@ -177,7 +177,7 @@
 	DBG("fbdev: get gamma");
 }
 
-static struct drm_fb_helper_funcs msm_fb_helper_funcs = {
+static const struct drm_fb_helper_funcs msm_fb_helper_funcs = {
 	.gamma_set = msm_crtc_fb_gamma_set,
 	.gamma_get = msm_crtc_fb_gamma_get,
 	.fb_probe = msm_fbdev_create,