iommu: arm-smmu: reverse order of bus/gdsc enable

Switch the order of gdsc enable and bus bandwidth voting. This is required
by the new hw clock/regulator resource manager on sdm845.

Change-Id: Ic47a953e01f01b57227497f61b76cd1ebc838278
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>