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

[ Upstream commit 00ef8885 ]

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

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20221125-mtk-iommu-v2-0-e168dff7d43e@chromium.org


[ joro: Fixed spelling in commit message ]
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>