crypto: chacha20 - Export common ChaCha20 helpers

As architecture specific drivers need a software fallback, export a
ChaCha20 en-/decryption function together with some helpers in a header
file.

Signed-off-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/chacha20poly1305.c

@@ -13,6 +13,7 @@
 #include <crypto/internal/hash.h>
 #include <crypto/internal/skcipher.h>
 #include <crypto/scatterwalk.h>
+#include <crypto/chacha20.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -23,8 +24,6 @@
 #define POLY1305_BLOCK_SIZE	16
 #define POLY1305_DIGEST_SIZE	16
 #define POLY1305_KEY_SIZE	32
-#define CHACHA20_KEY_SIZE	32
-#define CHACHA20_IV_SIZE	16
 #define CHACHAPOLY_IV_SIZE	12
 
 struct chachapoly_instance_ctx {