arm64: dma-mapping: Remove the notifier trick to handle early setting of dma_ops

With arch_setup_dma_ops now being called late during device's probe after the
device's iommu is probed, the notifier trick required to handle the early
setup of dma_ops before the iommu group gets created is not required.
So removing the notifier's here.

Signed-off-by: Sricharan R <sricharan@codeaurora.org>