drm/i915: Drop redunant null check from intel_get_frame_time_us()

intel_get_frame_time_us() is never called with a NULL crtc_state so
drop the redundant check.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231207193441.20206-7-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -893,7 +893,7 @@ transcoder_has_psr2(struct drm_i915_private *dev_priv, enum transcoder cpu_trans
 
 static u32 intel_get_frame_time_us(const struct intel_crtc_state *cstate)
 {
-	if (!cstate || !cstate->hw.active)
+	if (!cstate->hw.active)
 		return 0;
 
 	return DIV_ROUND_UP(1000 * 1000,