isdn/gigaset: missing break in do_facility_req

If we take the unsupported supplementary service notification mask
path, we end up falling through and overwriting the error code.
Insert a break statement to skip the remainder of the switch case
and proceed to sending the reply message.

Spotted with Coverity.
Reported-by: NDave Jones <davej@redhat.com>
Signed-off-by: NTilman Schmidt <tilman@imap.cc>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/isdn/gigaset/capi.c

@@ -1180,6 +1180,7 @@ static void do_facility_req(struct gigaset_capi_ctr *iif,
 				confparam[3] = 2;	/* length */
 				capimsg_setu16(confparam, 4,
 					       CapiSupplementaryServiceNotSupported);
+				break;
 			}
 			info = CapiSuccess;
 			confparam[3] = 2;	/* length */