intel/compiler: consistently use ifndef guards over pragma once

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Acked-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: Vedran Miletić <vedran@miletic.net>
Acked-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>

src/intel/compiler/brw_dead_control_flow.h

@@ -21,6 +21,11 @@
  * IN THE SOFTWARE.
  */
 
+#ifndef BRW_DEAD_CONTROL_FLOW_H
+#define BRW_DEAD_CONTROL_FLOW_H
+
 #include "brw_shader.h"
 
 bool dead_control_flow_eliminate(backend_shader *s);
+
+#endif /* BRW_DEAD_CONTROL_FLOW_H */