nfsd4: move principal name into svc_cred

Instead of keeping the principal name associated with a request in a
structure that's private to auth_gss and using an accessor function,
move it to svc_cred.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 9c3b9f0..12e4897 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -740,6 +740,7 @@
 	struct svc_cred	*cred = &rqstp->rq_cred;
 
 	cred->cr_group_info = NULL;
+	cred->cr_principal = NULL;
 	rqstp->rq_client = NULL;
 
 	if (argv->iov_len < 3*4)
@@ -805,6 +806,7 @@
 	int		len   = argv->iov_len;
 
 	cred->cr_group_info = NULL;
+	cred->cr_principal = NULL;
 	rqstp->rq_client = NULL;
 
 	if ((len -= 3*4) < 0)