ARM: shmobile: porter: add CAN0 DT support

Define the Porter board dependent part of the CAN0 device node.

This patch is  analogous to the commit 457acc4a ("ARM: shmobile:
henninger: add CAN0 DT support") as there are no differences between the
boards in this respect.

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