drivers: wifi: simplelink: socket() should return non-zero fds

simplelink_socket() is not returning non-zero socket file descriptors
when it succeeds. This leads to socket() to always return socket fd 0,
even when the network processor returns a non-zero fd.

This commit fixes simplelink_socket() to return the correct socket fd
when it succeeds in getting one from the network processor.

Fixes #12650

Signed-off-by: Vincent Wan <vincent.wan@linaro.org>

drivers/wifi/simplelink/simplelink_sockets.c

@@ -68,9 +68,12 @@ static int simplelink_socket(int family, int type, int proto)
 		if (retval < 0) {
 			retval = EPROTONOSUPPORT;
 			(void)sl_Close(sd);
+			goto exit;
 		}
 	}
 
+	retval = sd;
+
 exit:
 	return _SlDrvSetErrno(retval);
 }