crypto: api - Prune inclusions in crypto.h

We haven't used string.h since the memcpy calls were removed so
this patch removes its inclusion.  The file uaccess.h isn't needed
at all.  However, removing it reveals that we do need to add an
inclusion for refcount.h.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/linux/crypto.h

@@ -16,9 +16,8 @@
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/bug.h>
+#include <linux/refcount.h>
 #include <linux/slab.h>
-#include <linux/string.h>
-#include <linux/uaccess.h>
 #include <linux/completion.h>
 
 /*