drm/i915: Add intel_crtc_vblank_off()

We already have intel_crtc_vblank_on(). Add a counterpart so we
don't have to inline the disable+assert all over.
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191118164430.27265-3-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/display/intel_display.c

@@ -1843,6 +1843,12 @@ static void intel_crtc_vblank_on(const struct intel_crtc_state *crtc_state)
 	drm_crtc_vblank_on(&crtc->base);
 }
 
+static void intel_crtc_vblank_off(struct intel_crtc *crtc)
+{
+	drm_crtc_vblank_off(&crtc->base);
+	assert_vblank_disabled(&crtc->base);
+}
+
 static void intel_enable_pipe(const struct intel_crtc_state *new_crtc_state)
 {
 	struct intel_crtc *crtc = to_intel_crtc(new_crtc_state->uapi.crtc);
@@ -6760,8 +6766,7 @@ static void ironlake_crtc_disable(struct intel_crtc_state *old_crtc_state,
 
 	intel_encoders_disable(state, intel_crtc);
 
-	drm_crtc_vblank_off(crtc);
-	assert_vblank_disabled(crtc);
+	intel_crtc_vblank_off(intel_crtc);
 
 	intel_disable_pipe(old_crtc_state);
 
@@ -6810,8 +6815,7 @@ static void haswell_crtc_disable(struct intel_crtc_state *old_crtc_state,
 
 	intel_encoders_disable(state, intel_crtc);
 
-	drm_crtc_vblank_off(crtc);
-	assert_vblank_disabled(crtc);
+	intel_crtc_vblank_off(intel_crtc);
 
 	/* XXX: Do the pipe assertions at the right place for BXT DSI. */
 	if (!transcoder_is_dsi(cpu_transcoder))
@@ -7184,8 +7188,7 @@ static void i9xx_crtc_disable(struct intel_crtc_state *old_crtc_state,
 
 	intel_encoders_disable(state, intel_crtc);
 
-	drm_crtc_vblank_off(crtc);
-	assert_vblank_disabled(crtc);
+	intel_crtc_vblank_off(intel_crtc);
 
 	intel_disable_pipe(old_crtc_state);