drm/amdgpu/userq: rename suspend/resume callbacks

Rename to map and umap to better align with what is happening
at the firmware level and remove the extra level of indirection
in the MES userq code.

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