ARM: shmobile: porter: add SDHI0/2 DT support

Define the Porter board dependent part of the SDHI0/2 device nodes along
with the  necessary  voltage regulators (note that the Vcc regulators are
dummy -- they are required but don't actually exist on the board). Also,
GPIOs have to be used for the CD and WP signals due to the SDHI driver
constraints...

This patch is analogous to the commit 1299df03 ("ARM: shmobile:
henninger: add SDHI0/2 DT support") as there  are no differences between
those boards in this respect.

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