Revert "mdp4_overlay: Conditionally call ion_unmap_iommu()"

This reverts commit 58f36c0011669ad2c44785314609d0a8f979be99.
Revert "gpu: ion: Return an integer for ion_unmap_iommu()"

This reverts commit 1f1b563d22da897973b17f7847a792d1f713e80a.

Conflicts:
	drivers/gpu/ion/ion.c
mdp4_overlay: Only run loop for domain 2 & partition 2

Signed-off-by: Sultanxda <sultanxda@gmail.com>
Sultan_defconfig: v1.3.1