irqchip/irq-bcm2712-mip: Enable driver when ARCH_BCM2835 is enabled

The BCM2712 MIP driver is required for Raspberry PI5, but it's not
automatically enabled when ARCH_BCM2835 is enabled and depends on
ARCH_BRCMSTB.

ARCH_BCM2835 shares drivers with ARCH_BRCMSTB platforms, but Raspberry PI5
does not require the BRCMSTB specific drivers, which are selected via
ARCH_BRCMSTB.

Enable the interrupt controller for both ARCH_BRCMSTB and ARCH_BCM2835.

[ tglx: Massage changelog ]

Fixes: 32c6c054 ("irqchip: Add Broadcom BCM2712 MSI-X interrupt controller")
Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250416082523.179507-1-pbrobinson@gmail.com