drm/amd/pm: Remove unnecessary device state checks

For amdgpu_get_pp_force_state, amdgpu_get_pp_cur_state already takes
care of device state check. In other cases, values are returned from
driver cached variables and are not dependent on device state.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Feifei Xu <feifei.xu@amd.com>
Reviewed-by: Asad Kamal <asad.kamal@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>