IB/ipath: Enable reduced PIO update for HCAs that support it.

Newer HCAs have a threshold counter to reduce the number of DMAs the
chip makes to update the PIO buffer availability status bits.  This
patch enables the feature.

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/hw/ipath/ipath_kernel.h b/drivers/infiniband/hw/ipath/ipath_kernel.h
index 2447e85..cef3296 100644
--- a/drivers/infiniband/hw/ipath/ipath_kernel.h
+++ b/drivers/infiniband/hw/ipath/ipath_kernel.h
@@ -349,6 +349,7 @@
 	u32 ipath_lastrpkts;
 	/* pio bufs allocated per port */
 	u32 ipath_pbufsport;
+	u32 ipath_pioupd_thresh; /* update threshold, some chips */
 	/*
 	 * number of ports configured as max; zero is set to number chip
 	 * supports, less gives more pio bufs/port, etc.