NFS: Fix the selection of security flavours in Kconfig

NFS: Fix the selection of security flavours in Kconfig

Randy Dunlap reports:

ERROR: "svc_gss_principal" [fs/nfs/nfs.ko] undefined!

because in fs/nfs/Kconfig, NFS_V4 selects RPCSEC_GSS_KRB5
and/or in fs/nfsd/Kconfig, NFSD_V4 selects RPCSEC_GSS_KRB5.

RPCSEC_GSS_KRB5 does 5 selects, but none of these is enforced/followed
by the fs/nfs[d]/Kconfig configs:

	select SUNRPC_GSS
	select CRYPTO
	select CRYPTO_MD5
	select CRYPTO_DES
	select CRYPTO_CBC

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: J. Bruce Fields <bfields@fieldses.org>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>