HID: i2c-hid: introduce HID over i2c specification implementation

Microsoft published the protocol specification of HID over i2c:
http://msdn.microsoft.com/en-us/library/windows/hardware/hh852380.aspx

This patch introduces an implementation of this protocol.

This implementation does not includes the ACPI part of the specification.
This will come when ACPI 5.0 devices enumeration will be available.

Once the ACPI part is done, OEM will not have to declare HID over I2C
devices in their platform specific driver.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>