rtc: mt6397: select IRQ_DOMAIN instead of depending on it

IRQ_DOMAIN is a hidden (not user visible) symbol. Users cannot set
it directly thru "make *config", so drivers should select it instead
of depending on it if they need it.
Relying on it being set for a dependency is risky.

Consistently using "select" or "depends on" can also help reduce
Kconfig circular dependency issues.

Therefore, change the use of "depends on" for IRQ_DOMAIN to
"select" for RTC_DRV_MT6397.

Fixes: 04d3ba70

 ("rtc: mt6397: add IRQ domain dependency")
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Eddie Huang <eddie.huang@mediatek.com>
Cc: Sean Wang <sean.wang@mediatek.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mediatek@lists.infradead.org
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: linux-rtc@vger.kernel.org
Cc: Marc Zyngier <maz@kernel.org>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Peter Rosin <peda@axentia.se>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20240213050258.6167-1-rdunlap@infradead.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>