drm/amdgpu: validate return value of pm_runtime_get_sync

An invalid return value 'r' of the pm_runtime_get_sync
is r < 0, so fix the return value check and add proper
failure log and exit cleanly.

Successful refcount in userqueue creation to make sure
device remains in active state.

Fixes: 33d65834 ("drm/amdgpu/userq: handle runtime pm")
Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>