netfilter: ebtables: clean up initialization of buf

buf is initialized to buf_start and then set on the next statement
to buf_start + offsets[i].  Clean this up to just initialize buf
to buf_start + offsets[i] to clean up the clang build warning:
"Value stored to 'buf' during its initialization is never read"
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/bridge/netfilter/ebtables.c

@@ -2111,9 +2111,8 @@ static int size_entry_mwt(struct ebt_entry *entry, const unsigned char *base,
 	for (i = 0, j = 1 ; j < 4 ; j++, i++) {
 		struct compat_ebt_entry_mwt *match32;
 		unsigned int size;
-		char *buf = buf_start;
+		char *buf = buf_start + offsets[i];
 
-		buf = buf_start + offsets[i];
 		if (offsets[i] > offsets[j])
 			return -EINVAL;