ACPI: Clean up error code path in acpi_unbind_one()

The error code path in acpi_unbind_one() is unnecessarily complicated
(in particular, the err label is not really necessary) and the error
message printed by it is inaccurate (there's nothing called
'acpi_handle' in that function), so clean up those things.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Acked-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>