arm64: mm: dma-mapping: Modify handling for S1 bypass initialization

Since IOMMU domains that use S1 bypass do not need to know about
the DMA window of the device, move the logic for setting the
correct DMA ops for S1 bypass to an earlier point in time.

Change-Id: Ie80a44d888b4a786ea01270bc656635e0a65cdc5
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>