classmate-laptop: add support for Classmate PC ACPI devices

This add supports for devices like keyboard, backlight, tablet and
accelerometer.

This work is supported by International Syst S/A.

[randy.dunlap@oracle.com: cmpc_acpi: depends on ACPI]
[akpm@linux-foundation.org: readability tweaks]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>