iommu/exynos: Fix suspend/resume with IDENTITY domain

Commit bcb81ac6 ("iommu: Get DT/ACPI parsing into the proper probe
path") changed the sequence of probing the SYSMMU controller devices and
calls to arm_iommu_attach_device(), what results in resuming SYSMMU
controller earlier, when it is still set to IDENTITY mapping. Such change
revealed the bug in IDENTITY handling in the exynos-iommu driver. When
SYSMMU controller is set to IDENTITY mapping, data->domain is NULL, so
adjust checks in suspend & resume callbacks to handle this case
correctly.

Fixes: b3d14960 ("iommu/exynos: Implement an IDENTITY domain")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20250401202731.2810474-1-m.szyprowski@samsung.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>