bpf: add missing break in for the TCP_BPF_SNDCWND_CLAMP case

There appears to be a missing break in the TCP_BPF_SNDCWND_CLAMP case.
Currently the non-error path where val is greater than zero falls through
to the default case that sets the error return to -EINVAL. Add in
the missing break.

Detected by CoverityScan, CID#1449376 ("Missing break in switch")

Fixes: 13bf9641 ("bpf: Adds support for setting sndcwnd clamp")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NLawrence Brakmo <brakmo@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/filter.c

@@ -2867,6 +2867,7 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 					tp->snd_cwnd_clamp = val;
 					tp->snd_ssthresh = val;
 				}
+				break;
 			default:
 				ret = -EINVAL;
 			}