IB/ipath: Fix and recover TXE piobuf and PBC parity errors

We can sometimes trigger parity errors due to processor speculative
reads to our write-combined memory (mostly seen on Woodcrest).   Add a
stats counter for these.

Factored out the sendbuffererror buffer cancellation code so it can be
used in the new handling; suppress likely subsequent error messages if
within two jiffies of the cancellation.

Also restore 2 dropped TXE lines on hwe_bitsextant noticed while
debugging.

Signed-off-by: Bryan O'Sullivan <bryan.osullivan@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/hw/ipath/ipath_common.h b/drivers/infiniband/hw/ipath/ipath_common.h
index 382956d..a9b109a 100644
--- a/drivers/infiniband/hw/ipath/ipath_common.h
+++ b/drivers/infiniband/hw/ipath/ipath_common.h
@@ -141,8 +141,9 @@
 	 * packets if ipath not configured, etc.)
 	 */
 	__u64 sps_krdrops;
+	__u64 sps_txeparity; /* PIO buffer parity error, recovered */
 	/* pad for future growth */
-	__u64 __sps_pad[46];
+	__u64 __sps_pad[45];
 };
 
 /*