net: tcp: Remove redundant initialization of variable len

The variable len being initialized with a value that is never read, an
if statement is initializing it in both paths of the if statement.
The initialization is redundant and can be removed.

Cleans up clang scan build warning:
net/ipv4/tcp_ao.c:512:11: warning: Value stored to 'len' during its
initialization is never read [deadcode.DeadStores]
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Link: https://lore.kernel.org/r/20240216125443.2107244-1-colin.i.king@gmail.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

net/ipv4/tcp_ao.c

@@ -509,9 +509,9 @@ static int tcp_ao_hash_header(struct tcp_sigpool *hp,
 			      bool exclude_options, u8 *hash,
 			      int hash_offset, int hash_len)
 {
-	int err, len = th->doff << 2;
 	struct scatterlist sg;
 	u8 *hdr = hp->scratch;
+	int err, len;
 
 	/* We are not allowed to change tcphdr, make a local copy */
 	if (exclude_options) {