NFS: nfsacl_{encode,decode} should return signed integer

Clean up.

The nfsacl_encode() and nfsacl_decode() functions return negative
errno values, and each call site verifies that the returned value
is not negative.  Change the synopsis of both of these functions
to reflect this usage.

Document the synopsis and return values.

Reported-by: Trond Myklebust <trond.myklebust@netapp.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/nfsacl.h b/include/linux/nfsacl.h
index f321b57..fabcb1e 100644
--- a/include/linux/nfsacl.h
+++ b/include/linux/nfsacl.h
@@ -51,10 +51,10 @@
 	return w;
 }
 
-extern unsigned int
+extern int
 nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
 	      struct posix_acl *acl, int encode_entries, int typeflag);
-extern unsigned int
+extern int
 nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
 	      struct posix_acl **pacl);