drm/i915: Remove unnecessary null check in execlists_context_unqueue

commit 53292cdb ("drm/i915: Workaround
to avoid lite restore with HEAD==TAIL") added a check for req0 != null
which is unnecessary.

The only way req0 could be null is if the list was empty, and this is
already addressed at the beginning of execlists_context_unqueue().
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_lrc.c

@@ -427,7 +427,7 @@ static void execlists_context_unqueue(struct intel_engine_cs *ring)
 		 * WaIdleLiteRestore: make sure we never cause a lite
 		 * restore with HEAD==TAIL
 		 */
-		if (req0 && req0->elsp_submitted) {
+		if (req0->elsp_submitted) {
 			/*
 			 * Apply the wa NOOPS to prevent ring:HEAD == req:TAIL
 			 * as we resubmit the request. See gen8_emit_request()