drm/amd/pm: Fix get_if_active usage

If a device supports runtime pm, then pm_runtime_get_if_active returns 0
if a device is not active and 1 if already active. However, if a device
doesn't support runtime pm, the API returns -EINVAL. A device not
supporting runtime pm implies it's not affected by runtime pm and it's
active. Hence no need to get() to increment usage count. Remove < 0
return value check. Also, ignore runpm state to determine active status.
If the device is already in suspend state, disallow access.

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>