drm/amdgpu: Fix the code style warnings in gmc

Fix the code style warnings in gmc:
ERROR: space required after that ',' (ctx:VxV).

Signed-off-by: yipechai <YiPeng.Chai@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>