arm64: Properly clean up iommu-dma remnants

Thanks to the somewhat asymmetrical nature, while removing
iommu_setup_dma_ops() from the arch_setup_dma_ops() flow, I managed to
forget that arm64's teardown path was also specific to iommu-dma. Clean
that up to match, otherwise probe deferral will lead to the arch code
erroneously removing DMA ops set elsewhere.

Reported-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/linux-iommu/Zi_LV28TR-P-PzXi@eriador.lumag.spb.ru/
Fixes: b67483b3

 ("iommu/dma: Centralise iommu_setup_dma_ops()")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Acked-by: Will Deacon <will@kernel.org>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Link: https://lore.kernel.org/r/d4cc20cbb0c45175e98dd76bf187e2ad6421296d.1714472573.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>