net: Fix fall through warning in y2038 tstamp changes.

net/core/sock.c: In function 'sock_setsockopt':
net/core/sock.c:914:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
sock_set_flag(sk, SOCK_TSTAMP_NEW);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/core/sock.c:915:2: note: here
case SO_TIMESTAMPING_OLD:
^~~~

Fixes: 9718475e6908 ("socket: Add SO_TIMESTAMPING_NEW")
Reported-by: Stephen Rothwell <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/sock.c

···
 
 	case SO_TIMESTAMPING_NEW:
 		sock_set_flag(sk, SOCK_TSTAMP_NEW);
+		/* fall through */
 	case SO_TIMESTAMPING_OLD:
 		if (val & ~SOF_TIMESTAMPING_MASK) {
 			ret = -EINVAL;