ARM: bcm: Select BRCMSTB_L2_IRQ for bcm2835

The BCM2711 has a number of instances of interrupt controllers handled
by the driver behind the BRCMSTB_L2_IRQ Kconfig option (irq-brcmstb-l2).

Let's select that driver as part of the ARCH_BCM2835 Kconfig option.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>