[S390] qdio: improve inbound buffer acknowledgement

- Use automatic acknowledgement of incoming buffers in QEBSM mode
- Move ACK for non-QEBSM mode always to the newest buffer to prevent
  a race with qdio_stop_polling
- Remove the polling spinlock, the upper layer drivers return new buffers
  in the same code path and could not run in parallel
- Don't flood the error log in case of no-target-buffer-empty
- In handle_inbound we check if we would overwrite an ACK'ed buffer, if so
  advance the pointer to the oldest ACK'ed buffer so we don't overwrite an
  empty buffer in qdio_stop_polling

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/cio/qdio_perf.c b/drivers/s390/cio/qdio_perf.c
index bec0110..136d0f0 100644
--- a/drivers/s390/cio/qdio_perf.c
+++ b/drivers/s390/cio/qdio_perf.c
@@ -74,6 +74,8 @@
 	seq_printf(m, "\n");
 	seq_printf(m, "Number of fast requeues (outg. SBAL w/o SIGA)\t: %li\n",
 		   (long)atomic_long_read(&perf_stats.fast_requeue));
+	seq_printf(m, "Number of outbound target full condition\t: %li\n",
+		   (long)atomic_long_read(&perf_stats.outbound_target_full));
 	seq_printf(m, "Number of outbound tasklet mod_timer calls\t: %li\n",
 		   (long)atomic_long_read(&perf_stats.debug_tl_out_timer));
 	seq_printf(m, "Number of stop polling calls\t\t\t: %li\n",