ARM: dts: Beaglebone i2c definitions

The beaglebone family of boards contain two I2C busses enabled.
The first one with a baseboard identification EEPROM and a
cape I2C bus.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>