iommu-debug: Remove calls to iommu_enable_config_clocks

The iommu driver is responsible for enabling the required clocks
for map/unmap operations, not clients.

For the fastmap case, clocks are theoretically left enabled forever
after the initial attach, although in practice this does not occur
because there are no clocks required for Apps smmu.

Change-Id: Ibdfced1f62c79fbb3234d80bc9c65808d818c27a
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>