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>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20210111142309.193441-1-maxime@cerno.tech