Propagate the NFS 'fsc' mount option through NFS automounts of various types.

This is now required as commit:

	commit c02d7adf
	Author: Trond Myklebust <Trond.Myklebust@netapp.com>
	Date:   Mon Jun 22 15:09:14 2009 -0400

	NFSv4: Replace nfs4_path_walk() with VFS path lookup in a private namespace

uses VFS-driven automounting to reach all submounts barring the root, thus
preventing fscaching from being enabled on any submount other than the root.

This patch gets around that by propagating the NFS_OPTION_FSCACHE flag across
automounts.  If a uniquifier is supplied to a mount then this is propagated to
all automounts of that mount too.
Signed-off-by: David Howells <dhowells@redhat.com>
[Trond: Fixed up the definition of nfs_fscache_get_super_cookie for the
        case of #undef CONFIG_NFS_FSCACHE]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>