ARM: dts: AM33XX: Add default pinctrl binding for I2C device

Add pin control binding for I2C device nodes in all
board specific DT files (as per current usage),

EVM: Both i2c0 and i2c1
EVM-SK and Bone: Only i2c0

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Acked-by: Matt Porter <mporter@ti.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>