drm/amd/pm: Clean up errors in r600_dpm.h

Fix the following errors reported by checkpatch:

ERROR: that open brace { should be on the previous line
Signed-off-by: Ran Sun <sunran001@208suo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/legacy-dpm/r600_dpm.h

@@ -117,8 +117,7 @@ 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,