pds_core: Unmask adminq interrupt in work thread

Unmasking the interrupt during the pdsc_adminq_isr
is a bit early and could cause unnecessary interrupts.
Instead always unmask after processing the adminq
and notifyq in pdsc_work_thread()->pdsc_process_adminq().
Also, since we are always unmasking, there's no need
for the local credits variable in pdsc_process_adminq().

Signed-off-by: Brett Creeley <brett.creeley@amd.com>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>