libata-acpi.c: remove unneeded #if's

These #if's are unneeded since they:
- did anyway not handle the CONFIG_ACPI_DOCK_MODULE case correctly and
- this is already handled in include/acpi/acpi_drivers.h and
- it's now correctly handled in kconfig.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>