icnss: remove deprecated IOMMU APIs

IOMMU mapping APIs have been deprecated in favour of device
tree entries. Update ICNSS functions as required. Keep the
old API and structure for backward compatibility. They will be
removed once WLAN driver switch to the new APIs.

Change-Id: I7dc508dbea4a11eb125bd1ea737632a964d9713d
Signed-off-by: Sandeep Singh <sandsing@codeaurora.org>