omap: iommu: relax constraint value to allow CSWR

The iommu driver currently requests a latency constraint,
if configured in platform data, on the power domain it is
present in. These values are required only for OMAP4 and
beyond and is done to ensure the AMMU context is maintained
when the corresponding power domain goes to a low power state
during cpuidle path. The AMMU context is retained in CSWR, but
is lost in OSWR.

The current constraint value (10) for OMAP4+ is high and
restricts the power domain to remain in ON state as long as
the processor is active. This value is relaxed to 400 to
allow a lower power CSWR state during cpuidle path.

The context is saved and restored properly when suspending
the remote processor.

Change-Id: I89fd125f2244ae1691843c3c078aa6314a7ae8a6
Signed-off-by: Miguel Vadillo <vadillo@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>