mmc: tmio: Keep host active while SDIO IRQ is enabled

The host must be kept active to be able to serve SDIO IRQs, thus let's
prevent it from going inactive while SDIO IRQ is enabled.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>