drm/amd/amdgpu: Add missing mp_11_0_8_sh_mask.h header

The commit 2766534b added the offset
header but didn't add the masks.  This adds the masks based on what
was selected for the offsets.

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>