SUNRPC: Make cache_req::thread_wait an unsigned long

The second parameter of wait_for_completion_interruptible_timeout()
is a jiffies value whose type is "unsigned long". Avoid an
unnecessary and potentially fraught implicit type conversion at the
wait_for_completion_interruptible_timeout() call site in
cache_wait_req().
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/linux/sunrpc/cache.h

@@ -121,17 +121,17 @@ struct cache_detail {
 	struct net		*net;
 };
 
-
 /* this must be embedded in any request structure that
  * identifies an object that will want a callback on
  * a cache fill
  */
 struct cache_req {
 	struct cache_deferred_req *(*defer)(struct cache_req *req);
-	int thread_wait;  /* How long (jiffies) we can block the
-			   * current thread to wait for updates.
-			   */
+	unsigned long	thread_wait;	/* How long (jiffies) we can block the
+					 * current thread to wait for updates.
+					 */
 };
+
 /* this must be embedded in a deferred_request that is being
  * delayed awaiting cache-fill
  */