mmc: mtk-sd: don't hard-code interrupt trigger type

When using devicetree for configuration, interrupt trigger type
should be described in the dts file, not hard-coded in the C code.

The mtk-sd silicon in the mt7621 soc uses an active-high interrupt
and so cannot be used with the current code.

So replace IRQF_TRIGGER_LOW with IRQF_TRIGGER_NONE.

Also IRQF_ONESHOT is not needed - it is used for threaded interrupt
handlers, and this driver does not used a threaded interrupt handler.
So remove that setting.

Signed-off-by: NeilBrown <neil@brown.name>
Reviewed-by: Chaotian Jing <chaotian.jing@mediatek.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>