drm/amdgpu/gfx: delete stray tabs

These lines are indented one tab too far.  Delete the extra tabs.

Reviewed-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>