i2c: i801: Improve i801_acpi_probe/remove functions

By using ACPI_HANDLE() the handler argument can be retrieved directly.
Both address space handler functions check the handler argument and
return an error if it's NULL. This allows to further simplify the code.

Reviewed-by: Jean Delvare <jdelvare@suse.de>
Tested-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>