ARM: shmobile: armadillo-reference: Add st1232 pin mappings

Add pin mappings for the st1232 device to the device tree and reference
them as the default state for the device.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>