mmc: meson-gx: add SDIO interrupt support

Add SDIO interrupt support. Successfully tested on a S905X4-based
system (V3 register layout) with a BRCM4334 SDIO wifi module
(brcmfmac driver).

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/27bffe3c-e579-3581-95e8-2587733487d2@gmail.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>