NFS: move nfs_parsed_mount_data structure definition

In preparation for rearranging the nfs mount argument passing, make the
nfs_parsed_mount_data struct visible across nfs kernel files.

Signed-off-by: Tom Talpey <tmt@netapp.com>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>