Switch all register list clients to the new MC*Iterator interface.
No functional change intended.
Sorry for the churn. The iterator classes are supposed to help avoid
giant commits like this one in the future. The TableGen-produced
register lists are getting quite large, and it may be necessary to
change the table representation.
This makes it possible to do so without changing all clients (again).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157854
91177308-0d34-0410-b5e6-
96231b3b80d8