hid: Import iichid - I2C transport backend for HID subsystem
This implements hid_if.m methods for HID-over-I2C protocol [1].
Following kernel options are added:
IICHID_SAMPLING - Enable support for a sampling mode as interrupt
resource acquisition is not always possible in a case
of GPIO interrupts.
IICHID_DEBUG - Enable debug output.
The module is based on prior Marc Priggemeyer work (D16698).
[1] http://download.microsoft.com/download/7/d/d/
7dd44bb7-2a7a-4505-ac1c-
7227d3d96d5b/hid-over-i2c-protocol-spec-v1-0.docx
Differential revision: https://reviews.freebsd.org/D27892