ARM: mach-shmobile: sh7377 Enable SDIO IRQs

This patch enables interrupt generation for SDIO IRQs
of the SDHI block on the sh7377 aka G4 processor. Use
together with a recent SDHI driver using TMIO_MMC_SDIO_IRQ
and with the MMC_CAP_SDIO_IRQ flag in the board code.

The G4EVM specific SDHI platform data is also updated to
flag SDIO capabilities.

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