HID: i2c-hid: acpi: Get ACPI companion only once and reuse it

Currently the ACPI companion and handle are retrieved and checked
a few times in different functions. Instead get ACPI companion only
once and reuse it everywhere.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>