drm/radeon: Clean up errors in r600_dpm.h

Fix the following errors reported by checkpatch:

ERROR: open brace '{' following enum go on the same line
Signed-off-by: GuoHua Chen <chenguohua_716@163.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/r600_dpm.h

@@ -119,8 +119,7 @@ enum r600_display_watermark {
 	R600_DISPLAY_WATERMARK_HIGH = 1,
 };
 
-enum r600_display_gap
-{
+enum r600_display_gap {
     R600_PM_DISPLAY_GAP_VBLANK_OR_WM = 0,
     R600_PM_DISPLAY_GAP_VBLANK       = 1,
     R600_PM_DISPLAY_GAP_WATERMARK    = 2,