drm/amd/powerplay: fix misspelling in header guard

In smu7_clockpowergating.h, the #ifndef statement which prevents
multiple inclusions of the header file uses _SMU7_CLOCK_POWER_GATING_H_
but the following #define statement uses _SMU7_CLOCK__POWER_GATING_H_.

Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/hwmgr/smu7_clockpowergating.h

@@ -22,7 +22,7 @@
  */
 
 #ifndef _SMU7_CLOCK_POWER_GATING_H_
-#define _SMU7_CLOCK__POWER_GATING_H_
+#define _SMU7_CLOCK_POWER_GATING_H_
 
 #include "smu7_hwmgr.h"
 #include "pp_asicblocks.h"