ARM: shmobile: porter: enable PCIe

Enable the PCIe controller and clock for the Porter board.

This patch is analogous to the commit 485f3ce6 ("ARM: shmobile:
henninger: Enable PCIe Controller & PCIe bus clock") 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>