staging/lustre: Remove index file transfer structures

struct idx_info, struct lu_idxpage, lustre_swab_idx_info,
request formats and related defines are all unused and could
only happen for between-servers communications, so remove them
from the client code.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>