MFC r256959:

  Add the Raspberry Pi BSC (I2C compliant) controller driver.

  Reviewed by:	rpaulo

MFC r256961:

  Enable the build of OFW I2C bus for FDT systems.

MFC r258045:

  As all the IIC controllers on system uses the same 'iichb' prefix we cannot
  rely only on checking the device unit to indentify the BSC unit we are
  attaching to.  Make use of the device base address to identify our BSC unit.

MFC r259127:

  Bring the RPi I2C driver in line with ti_i2c.  Make it treat any slave
  address as a 7-bit address.

Approved by:	adrian (mentor)