cifs: teach signing routines how to deal with arrays of pages in a smb_rqst

Use the smb_send_rqst helper function to kmap each page in the array
and update the hash for that chunk.

Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 381dbb7..b609734 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -251,7 +251,7 @@
  * The page will be kmapped and the address placed into iov_base. The length
  * will then be adjusted according to the ptailoff.
  */
-static void
+void
 cifs_rqst_page_to_kvec(struct smb_rqst *rqst, unsigned int idx,
 			struct kvec *iov)
 {