PKCS#7: fix unitialized boolean 'want'

The boolean want is not initialized and hence garbage. The default should
be false (later it is only set to true on tne sinfo->authattrs check).

Found with static analysis using CoverityScan

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David Howells <dhowells@redhat.com>

crypto/asymmetric_keys/pkcs7_parser.c

@@ -87,7 +87,7 @@ EXPORT_SYMBOL_GPL(pkcs7_free_message);
 static int pkcs7_check_authattrs(struct pkcs7_message *msg)
 {
 	struct pkcs7_signed_info *sinfo;
-	bool want;
+	bool want = false;
 
 	sinfo = msg->signed_infos;
 	if (sinfo->authattrs) {