Remove references to the cortex-a9-mp CPU.

This CPU definition is redundant. The Cortex-A9 is defined as
supporting multiprocessing extensions. Remove references to this CPU.

This CPU was recently removed from LLVM. See http://reviews.llvm.org/D6057

Change-Id: I62ae7cc656fcae54fbaefc4b6976e77e694a8678

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@221458 91177308-0d34-0410-b5e6-96231b3b80d8