iommu/arm-smmu: Make fault triggering more reliable

We're currently disabling clocks/power immediately after writing to
FSRRESTORE, but if the fault is not handled before we disable the
clocks/power then the fault could be lost.  Add a 1-second sleep after
writing to FSRRESTORE to give the interrupt time to fire before turning
clocks/power back off.

Change-Id: Ieeba49686da5da92e43f03c3c593166592184433
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>