Enable and disable the IOMMU clocks for each high-level mapping operation rather than leaving the clocks enabled between attach-time and detach-time even if no IOMMU operations are being done. Change-Id: I4cde881992b8cd77fb4ea7e8dc1c003f639d15b6 Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>