crypto: crypto_user - fix sparse warnings (symbol was not declared, should be static?)

Fix "symbol 'x' was not declared. Should it be static?" sparse warnings.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c
index ba2c611..b590471 100644
--- a/crypto/crypto_user.c
+++ b/crypto/crypto_user.c
@@ -30,7 +30,7 @@
 
 #include "internal.h"
 
-DEFINE_MUTEX(crypto_cfg_mutex);
+static DEFINE_MUTEX(crypto_cfg_mutex);
 
 /* The crypto netlink socket */
 static struct sock *crypto_nlsk;