crypto: user - forward declare crypto_nlsk

Move the declaration of crypto_nlsk into internal/cryptouser.h.  This
fixes the following sparse warning:

    crypto/crypto_user_base.c:41:13: warning: symbol 'crypto_nlsk' was not declared. Should it be static?

Cc: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/crypto/internal/cryptouser.h

@@ -1,6 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #include <net/netlink.h>
 
+extern struct sock *crypto_nlsk;
+
 struct crypto_alg *crypto_alg_match(struct crypto_user_alg *p, int exact);
 
 #ifdef CONFIG_CRYPTO_STATS