drm: Add acquire ctx to ->gamma_set hook

Atomic helpers really want this instead of the hacked-up legacy
backoff trick, which unfortunately prevents drivers from using their
own private drm_modeset_locks.

Aside: There's a few atomic drivers (nv50, vc4, soon vmwgfx) which
don't yet use the new atomic color mgmt/gamma table stuff. Would be
nice if they could switch over and just hook up
drm_atomic_helper_legacy_gamma_set() instead.

Cc: Dave Airlie <airlied@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Sinclair Yeh <syeh@vmware.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Eric Anholt <eric@anholt.net>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170403083304.9083-13-daniel.vetter@ffwll.ch

drivers/gpu/drm/nouveau/dispnv04/crtc.c

@@ -788,7 +788,8 @@ nv_crtc_disable(struct drm_crtc *crtc)
 
 static int
 nv_crtc_gamma_set(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
-		  uint32_t size)
+		  uint32_t size,
+		  struct drm_modeset_acquire_ctx *ctx)
 {
 	struct nouveau_crtc *nv_crtc = nouveau_crtc(crtc);
 	int i;