QCOM GENI I²C driver

This is a from scratch, minimally viable, I²C driver for QCOM's
GENI serial engine.

No QCOM documentation is available, so other FOSS device drivers
were consulted to figure things out

The driver works on T14s G6 "Snapdragon" hardware, to such a degree
that ACPI clients and HID devices work (polling mode & needs
modifications to iichid)

Differential Revision: https://reviews.freebsd.org/D49676
Reviews by: adrian