iommu/rockchip: Move irq request past pm_runtime_enable

Enabling the interrupt early, before power has been applied to the
device, can result in an interrupt being delivered too early if:

- the IOMMU shares an interrupt with a VOP
- the VOP has a pending interrupt (after a kexec, for example)

In these conditions, we end-up taking the interrupt without
the IOMMU being ready to handle the interrupt (not powered on).

Moving the interrupt request past the pm_runtime_enable() call
makes sure we can at least access the IOMMU registers. Note that
this is only a partial fix, and that the VOP interrupt will still
be screaming until the VOP driver kicks in, which advocates for
a more synchronized interrupt enabling/disabling approach.

Fixes: 0f181d3c

 ("iommu/rockchip: Add runtime PM support")
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>