iommu/mediatek: Fix crash on isr after kexec()

In the Linux kernel, the following vulnerability has been resolved:

iommu/mediatek: Fix crash on isr after kexec()

If the system is rebooted via isr(), the IRQ handler might

be triggered before the domain is initialized. Resulting on

an invalid memory access error.

Fix:

[ 0.500930] Unable to handle kernel read from unreadable memory at virtual address 0000000000000070

[ 0.501166] Call trace:

[ 0.501174] report_iommu_fault+0x28/0xfc

[ 0.501180] mtk_iommu_isr+0x10c/0x1c0

[ joro: Fixed spelling in commit message ]