libata: use ata_port_printk() in ata_wait_idle()

ata_wait_idle() identified controller by printing out the address of
the Status register.  This is bogus because 1. it's iomapped address
2. some controllers don't have Status register and don't initialize
the field.  Use ata_port_printk() instead.

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