hwmon: (asus_atk0110) Refactor the code

Refactor the code of the new style interface around GGRP (enumeration) and
GITM (read) helpers to mimic ASL code. Also switch the read path to use
dynamic buffers (handled by ACPI core) since ASUS expanded the return buffer
(ASBF) in newer boards (e.g. P7P55D).

Signed-off-by: Luca Tettamanti <kronos.it@gmail.com>
Tested-by: Robert Hancock <hancockrwd@gmail.com>
Tested-by: Thomas Backlund <tmb@mandriva.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>