drm/amdgpu: Clean up errors in umc_v6_0.c

Fix the following errors reported by checkpatch:

ERROR: space required after that ',' (ctx:VxV)
Signed-off-by: chenxuebing <chenxb_99091@126.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/umc_v6_0.c

@@ -25,7 +25,7 @@
 
 static void umc_v6_0_init_registers(struct amdgpu_device *adev)
 {
-	unsigned i,j;
+	unsigned i, j;
 
 	for (i = 0; i < 4; i++)
 		for (j = 0; j < 4; j++)