nfsd: move nfsd/auth.h into fs/nfsd

This header is used only in a few places in fs/nfsd, so there seems to
be little point to having it in include/.  (Thanks to Robert Day for
pointing this out.)

Cc: Robert P. J. Day <rpjday@crashcourse.ca>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/nfsfh.c

@@ -22,6 +22,7 @@
 #include <linux/sunrpc/svc.h>
 #include <linux/sunrpc/svcauth_gss.h>
 #include <linux/nfsd/nfsd.h>
+#include "auth.h"
 
 #define NFSDDBG_FACILITY		NFSDDBG_FH