mmc: tmio_mmc: implement SDIO IRQ support

This patch implements SDIO IRQ support for mfds which
announce the TMIO_MMC_SDIO_IRQ flag for tmio_mmc.
If MMC_CAP_SDIO_IRQ is also set SDIO IRQ signalling is activated.
Tested with a b43-based wireless SDIO card and sh_mobile_sdhi.

Signed-off-by: Arnd Hannemann <arnd@arndnet.de>
Signed-off-by: Chris Ball <cjb@laptop.org>