ANDROID: kconfig: Add MTK_IRQ dedicated for irq-mtk

MTK_IRQ replaces the ARCH_MEDIATEK in Makefile adding
irq-mtk-sysirq.o and irq-mtk-cirq.o in drivers/irqchip
to compilation. Using a dedicated config makes enabling
ARCH_MEDIATEK from vendor fragment possible because explicitly
unsetting MTK_IRQ saves us from adding some core functionality
by default.

Bug: 432487220

Change-Id: I586138b099780509d83c3ba0894099fcd006e704
Signed-off-by: Zyta Szpak <zyta@google.com>