drm/amd: Move AMD_IS_APU check for ASPM into top level function

drm/amd: Move AMD_IS_APU check for ASPM into top level function

There is no need for every ASIC driver to perform the same check.
Move the duplicated code into amdgpu_device_should_use_aspm().

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>