drm/xe: Fix header guard warning

Additional underscore in the header guard causes the build to fail with:

drivers/gpu/drm/xe/xe_hw_engine_class_sysfs.h:6:9: error: '_XE_ENGINE_CLASS_SYSFS_H_' is used as a header guard here, followed by #define of a different macro [-Werror,-Wheader-guard]
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20231129214509.1174116-1-michal.winiarski@intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_hw_engine_class_sysfs.h

@@ -4,7 +4,7 @@
  */
 
 #ifndef _XE_ENGINE_CLASS_SYSFS_H_
-#define _XE_ENGINE_CLASS_SYSFS_H__
+#define _XE_ENGINE_CLASS_SYSFS_H_
 
 #include <linux/kobject.h>