drm/amd/display: Clean up some inconsistent indenting

Eliminate the follow smatch warning:

drivers/gpu/drm/amd/amdgpu/../display/dmub/src/dmub_srv.c:622
dmub_srv_cmd_execute() warn: inconsistent indenting.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>