[PATCH] libata: add probeinit component operation to ata_drive_probe_reset()

This patch adds probeinit component operation to
ata_drive_probe_reset().  If present, this new operation is called
before performing any reset.  The operations's roll is to prepare @ap
for following probe-reset operations.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>