Add the I2C driver for the Armada 37x0.

This controller is a bit tricky as the STOP condition must be indicated in
the last tranferred byte, some devices will not like the repeated start
behavior of this controller. A proper fix to this issue is in the works.

This driver works in polling mode, can be used early in the boot (required
in some cases).

Tested on espressobin/SG-1100 and the SG-3200.

Obtained from: pfSense
Sponsored by: Rubicon Communications, LLC (Netgate)