ata: pata_at91.c bugfix for initial_timing initialisation

The "struct ata_timing" must contain 10 members, but ".dmack_hold" member was
forgotten for "initial_timing" initialisation. This patch fixes such a problem.

Signed-off-by: Igor Plyatov <plyatov@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>