ARM: shmobile: henninger: add I2C2 DT support

Define the Henninger board dependent part of the I2C2 device node.

Based on the Koelsch I2C2 device tree patch by Wolfram Sang.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>