drm/amdgpu/gfx10: drop redundant se/sh selection

we already selected se/sh at the beginning of the for loop

Signed-off-by: Xiaojie Yuan <xiaojie.yuan@amd.com>
Reviewed-by: Jack Xiao <Jack.Xiao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>