ARM Scheduler Model: Add resources instructions, map resources in subtargets

Reapply r177968:
After commit 178074 we can now have undefined scheduler variants.

Move the CortexA9 resources into the CortexA9 SchedModel namespace. Define
resource mappings under the CortexA9 SchedModel. Define resources and mappings
for the SwiftModel.

Incooperate Andrew's feedback.