Input: mtk-pmic-keys - use get_irq_byname() instead of index

Input: mtk-pmic-keys - use get_irq_byname() instead of index

Some pmics of the mt6397 family (such as MT6358), have two IRQs per
physical key: one for press event, another for release event.

The mtk-pmic-keys driver assumes that each key only has one
IRQ. The key index and the RES_IRQ resource index have a 1/1 mapping.

This won't work for MT6358, as we have multiple resources (2) for one key.

To prepare mtk-pmic-keys to support MT6358, retrieve IRQs by name
instead of by index.

Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20220121140323.4080640-2-mkorpershoek@baylibre.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>