crypto: api - Move module sig ifdef into accessor function

Currently we're hiding mod->sig_ok under an ifdef in open code.
This patch adds a module_sig_ok accessor function and removes that
ifdef.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/crypto/algapi.c b/crypto/algapi.c
index a60f626..f835f43 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -43,12 +43,9 @@
 
 static inline void crypto_check_module_sig(struct module *mod)
 {
-#ifdef CONFIG_CRYPTO_FIPS
-	if (fips_enabled && mod && !mod->sig_ok)
+	if (fips_enabled && mod && !module_sig_ok(mod))
 		panic("Module %s signature verification failed in FIPS mode\n",
 		      mod->name);
-#endif
-	return;
 }
 
 static int crypto_check_alg(struct crypto_alg *alg)