cifs: Fix TCP_Server_Info::credits to be signed

Fix TCP_Server_Info::credits to be signed, just as echo_credits and
oplock_credits are.  This also fixes what ought to get at least a
compilation warning if not an outright error in *get_credits_field() as a
pointer to the unsigned server->credits field is passed back as a pointer
to a signed int.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cifs@vger.kernel.org
Cc: stable@vger.kernel.org
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Acked-by: Pavel Shilovskiy <pshilovskiy@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: dhowells

fs/smb/client/cifsglob.h

@@ -732,7 +732,7 @@ struct TCP_Server_Info {
 	bool nosharesock;
 	bool tcp_nodelay;
 	bool terminate;
-	unsigned int credits;  /* send no more requests at once */
+	int credits;  /* send no more requests at once */
 	unsigned int max_credits; /* can override large 32000 default at mnt */
 	unsigned int in_flight;  /* number of requests on the wire to server */
 	unsigned int max_in_flight; /* max number of requests that were on wire */