ACPI: OSL: Use deferred unmapping in acpi_os_unmap_generic_address()

There is no reason (knwon to me) why any of the existing users of
acpi_os_unmap_generic_address() would need to wait for the unused
memory mappings left by it to actually go away, so use the deferred
unmapping of ACPI memory introduced previously in that function.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>