irqchip/irq-brcmstb-l2: Fix section mismatch

irqchip/irq-brcmstb-l2: Fix section mismatch

[ Upstream commit bbe1775924478e95372c2f896064ab6446000713 ]

Platform drivers can be probed after their init sections have been
discarded so the irqchip init callbacks must not live in init.

Fixes: 51d9db5c8fbb ("irqchip/irq-brcmstb-l2: Switch to IRQCHIP_PLATFORM_DRIVER")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>