[PATCH] libata: cosmetic update to ata_bus_probe()

Move ata_set_mode() failure handling outside of ap->ops->set_mode if
clause such that it can handle ap->ops->set_mode failures after it's
updated.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>