ARM: mach-shmobile: ap4evb: fix write protect for SDHI1

SDHI1 on AP4EVB has no pin to detect write protection of a card.
This had the result that a card inserted in this slot was always detected
as read only. This patch adds the corresponding flag to disable
write protection detection for SDHI1.

Signed-off-by: Arnd Hannemann <arnd@arndnet.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>