ARM: dts: BCM5301X: Add I2C support to the DT

Add I2C support to the bcm5301x Device Tree.  Since no driver changes
are needed to enable this hardware, only the device tree changes are
required to make this functional.

Signed-off-by: Jon Mason <jonmason@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>