mmc: host: tmio: refactor calls to sdio irq

tmio_mmc_sdio_irq() is not used as a seperate irq handler anymore, so we
can make it similar to the other irq helper functions, namely:

* only give the host as argument function which is what it really needs
* prefix function name with __

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>