iommu/rockchip: Free irqs in shutdown handler

In the iommu's shutdown handler we disable runtime-pm which could
result in the irq-handler running unclocked and since commit
    3fc7c5c0 ("iommu/rockchip: Handle errors returned from PM framework")
we warn about that fact.

This can cause warnings on shutdown on some Rockchip machines, so
free the irqs in the shutdown handler before we disable runtime-pm.

Reported-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Fixes: 3fc7c5c0 ("iommu/rockchip: Handle errors returned from PM framework")
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>