msm: Move subsystem map specific code to the subsystem map file

Code to translate between the old style subsystem map ids and
newer domain/partition numbers is no longer dependent on anything
in iommu_domains.c. Move it to the subsystem_map file to better
separate the old code from the new code.

Change-Id: I899a3215f17b7b8c55969086389b89c4401bea3f
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>