vf_i2c: split up and add ACPI attachments in addition to FDT
Move the code from the arm specific to the iicbus controller directory.
Split up between general logic and bus attachment code.
Add support for ACPI attachment in addition to FDT.
Tested by: bz (LS1088a FDT), Pierre-Luc Drouin (Honeycomb, ACPI)
Based on: D24917 by Val Packett (initial early version)
(cherry picked from commit 5ca8e32633c4ffbbcd6762e5888b6a4ba0708c6c)