drm/amdgpu/mes12: add conversion for priority levels

Convert driver priority levels to MES11 priority levels.
At the moment they are the same, but they may not always
be.

Reviewed-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Jesse.Zhang <Jesse.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>