ARM: dts: bcm27xx: Add i2c_arm/vc and friends

Since there is now a dedicated dts file for the rev1 Model B (the only
Pi to drive the primary camera with i2c1), move the creation of the
i2c_arm, i2c_vc and i2c labels, aliases and overrides into the base dts
files.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>