opencrypto: Annotate hmac_init_(i|o)pad() to make auth_hash const

This makes them friendlier to drivers that try to use const pointers
whenever possible in their internal structures.

Reviewed by:	jhb
Sponsored by:	Rubicon Communications, LLC (Netgate)
Differential Revision:	https://reviews.freebsd.org/D26901

sys/opencrypto/crypto.c

@@ -411,8 +411,8 @@ crypto_terminate(struct proc **pp, void *q)
 }
 
 static void
-hmac_init_pad(struct auth_hash *axf, const char *key, int klen, void *auth_ctx,
-    uint8_t padval)
+hmac_init_pad(const struct auth_hash *axf, const char *key, int klen,
+    void *auth_ctx, uint8_t padval)
 {
 	uint8_t hmac_key[HMAC_MAX_BLOCK_LEN];
 	u_int i;
@@ -442,7 +442,7 @@ hmac_init_pad(struct auth_hash *axf, const char *key, int klen, void *auth_ctx,
 }
 
 void
-hmac_init_ipad(struct auth_hash *axf, const char *key, int klen,
+hmac_init_ipad(const struct auth_hash *axf, const char *key, int klen,
     void *auth_ctx)
 {
 
@@ -450,7 +450,7 @@ hmac_init_ipad(struct auth_hash *axf, const char *key, int klen,
 }
 
 void
-hmac_init_opad(struct auth_hash *axf, const char *key, int klen,
+hmac_init_opad(const struct auth_hash *axf, const char *key, int klen,
     void *auth_ctx)
 {
 

sys/opencrypto/cryptodev.h

@@ -683,9 +683,9 @@ SYSCTL_DECL(_kern_crypto);
 /* Helper routines for drivers to initialize auth contexts for HMAC. */
 struct auth_hash;
 
-void	hmac_init_ipad(struct auth_hash *axf, const char *key, int klen,
+void	hmac_init_ipad(const struct auth_hash *axf, const char *key, int klen,
     void *auth_ctx);
-void	hmac_init_opad(struct auth_hash *axf, const char *key, int klen,
+void	hmac_init_opad(const struct auth_hash *axf, const char *key, int klen,
     void *auth_ctx);
 
 /*