sh: Add SDHI power control support to Ecovec

This patch adds support for SDHI power control to the
Ecovec board. Platform data and power control callbacks
for SDHI0 and SDHI1 are added. Power is by default off.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>