drm/i915: Polish intel_tv_mode_valid()

Drop the tv_mode NULL check since intel_tv_mode_find() never
actually returns NULL, and flip the condition around so that
the MODE_OK case is at the end, which is customary to all
the other .mode_valid() implementations.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191001154629.11063-2-ville.syrjala@linux.intel.comReviewed-by: José Roberto de Souza <jose.souza@intel.com>

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

@@ -961,11 +961,10 @@ intel_tv_mode_valid(struct drm_connector *connector,
 		return MODE_CLOCK_HIGH;
 
 	/* Ensure TV refresh is close to desired refresh */
-	if (tv_mode && abs(tv_mode->refresh - drm_mode_vrefresh(mode) * 1000)
-				< 1000)
-		return MODE_OK;
-
+	if (abs(tv_mode->refresh - drm_mode_vrefresh(mode) * 1000) >= 1000)
 		return MODE_CLOCK_RANGE;
+
+	return MODE_OK;
 }
 
 static int