IB/ipath: Add locking for interrupt use of ipath_pd contexts vs free

Fixes timing race resulting in panic.  Not a performance sensitive path.

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_kernel.h

@@ -477,6 +477,8 @@ struct ipath_devdata {
 	spinlock_t ipath_kernel_tid_lock;
 	spinlock_t ipath_user_tid_lock;
 	spinlock_t ipath_sendctrl_lock;
+	/* around ipath_pd and (user ports) port_cnt use (intr vs free) */
+	spinlock_t ipath_uctxt_lock;
 
 	/*
 	 * IPATH_STATUS_*,