libata-acpi: clean up parameters and misc stuff

This patch cleans up libata-acpi such that it looks similar to other
libata files.  This patch doesn't introuce any behavior changes.

* make libata-acpi functions take ata_device instead of ata_port +
  device index
* s/atadev/dev/
* de-indent local variable declarations

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