Given the service name and timestamp id, this assembler macro
calculates the offset into a memory region where the per-cpu timestamp
value is located.
Change-Id: I47f6dfa2a17be182675e2ca0489d6eed42433209
More headers will be needed soon so better to move these to their own
directory to avoid cluttering include/lib.
Change-Id: I6a72dc5b602d6f51954cf60aadd1beb52a268670