mptcp: fix bogus socket flag values

Dan Carpenter reports static checker warnings due to bogus BIT() usage:

net/mptcp/subflow.c:571 subflow_write_space() warn: test_bit() takes a bit number
net/mptcp/subflow.c:694 subflow_state_change() warn: test_bit() takes a bit number
net/mptcp/protocol.c:261 ssk_check_wmem() warn: test_bit() takes a bit number
[..]

This is harmless (we use bits 1 & 2 instead of 0 and 1), but would
break eventually when adding BIT(5) (or 6, depends on size of 'long').

Just use 0 and 1, the values are only passed to test/set/clear_bit
functions.

Fixes: 648ef4b8 ("mptcp: Implement MPTCP receive path")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/protocol.h

@@ -56,8 +56,8 @@
 #define MPTCP_DSS_FLAG_MASK	(0x1F)
 
 /* MPTCP socket flags */
-#define MPTCP_DATA_READY	BIT(0)
-#define MPTCP_SEND_SPACE	BIT(1)
+#define MPTCP_DATA_READY	0
+#define MPTCP_SEND_SPACE	1
 
 /* MPTCP connection sock */
 struct mptcp_sock {