omap: iommu: apply latency constraint based on power domain

When the iommu is taken out of reset, a latency constraint is
set to avoid its power domain going to retention/off. The iommus
for DSP and M3 reside in DSP and Core power domains respectively,
and therefore the API for setting the constraints is different.
This patch uses the appropriate API depending on the iommu (power
domain) the latency constraint is being applied on.

Change-Id: I3fa4485b3c405aa10c32a3fe0b7ac694d484ee21
Signed-off-by: Juan Gutierrez <jgutierrez@ti.com>
Signed-off-by: Subramaniam C.A <subramaniam.ca@ti.com>

Conflicts:
	arch/arm/plat-omap/iommu.c