drm/imx: Constify function pointer structs

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

 drivers/gpu/drm/imx/imxdrm.ko:
-.rodata                      624
+.rodata                      652
-.data                        372
+.data                        344

 drivers/gpu/drm/imx/imx-ipuv3-crtc.ko:
-.rodata                      224
+.rodata                      280
-.data                        184
+.data                        128

 drivers/gpu/drm/imx/imx-ldb.ko:
-.rodata                      660
+.rodata                      784
-.data                        240
+.data                        116

 drivers/gpu/drm/imx/imx-tve.ko:
-.rodata                      400
+.rodata                      524
-.data                        416
+.data                        292

 drivers/gpu/drm/imx/parallel-display.ko:
-.rodata                      400
+.rodata                      524
-.data                        216
+.data                         92

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/1450178476-26284-22-git-send-email-boris.brezillon@free-electrons.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/imx/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3-crtc.c
index 4ab841e..30a5718 100644
--- a/drivers/gpu/drm/imx/ipuv3-crtc.c
+++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
@@ -270,7 +270,7 @@
 	ipu_fb_enable(ipu_crtc);
 }
 
-static struct drm_crtc_helper_funcs ipu_helper_funcs = {
+static const struct drm_crtc_helper_funcs ipu_helper_funcs = {
 	.dpms = ipu_crtc_dpms,
 	.mode_fixup = ipu_crtc_mode_fixup,
 	.mode_set = ipu_crtc_mode_set,