crypto: doc - fix header file name

Fixes: 8bc618d6 ("crypto: doc - Use ahash")
Signed-off-by: NBaruch Siach <baruch@tkos.co.il>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Documentation/crypto/api-intro.txt

@@ -49,7 +49,7 @@ under development.
 
 Here's an example of how to use the API:
 
-	#include <crypto/ahash.h>
+	#include <crypto/hash.h>
 	#include <linux/err.h>
 	#include <linux/scatterlist.h>