crypto: engine - move crypto engine to its own header

This patch move the whole crypto engine API to its own header
crypto/engine.h.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/crypto_engine.c b/crypto/crypto_engine.c
index a55c82d..795b6f9 100644
--- a/crypto/crypto_engine.c
+++ b/crypto/crypto_engine.c
@@ -14,6 +14,7 @@
 
 #include <linux/err.h>
 #include <linux/delay.h>
+#include <crypto/engine.h>
 #include "internal.h"
 
 #define CRYPTO_ENGINE_MAX_QLEN 10