ARM: mach-shmobile: sh7372 Enable SDIO IRQs

This patch enables the interrupt generation for SDIO IRQs
of the sdhi controllers of the SoC. To make sure interrupts
are handled announce the MMC_CAP_SDIO_IRQ capability
on AP4EVB. Tested with a b43-based SDIO wireless card.

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