[ARM] Custom machine-scheduler. NFCI.

This patch creates a customised machine-scheduler for ARM targets,
so that subsequently DAG mutations etc can be added.
Reviewed by: hahn, rengolin, rovka. 
Differential Revision: https://reviews.llvm.org/D34039



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305078 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed