amdgpu/drm: remove psp access on navi10 for sriov

Navi ASICs don't require to access through PSP to osssys registers.
This on SR-IOV configuration.

Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>