Add "Restored" flag to CalleeSavedInfo

Add "Restored" flag to CalleeSavedInfo

The liveness-tracking code assumes that the registers that were saved
in the function's prolog are live outside of the function. Specifically,
that registers that were saved are also live-on-exit from the function.
This isn't always the case as illustrated by the LR register on ARM.

Differential Revision: https://reviews.llvm.org/D36160

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310619 91177308-0d34-0410-b5e6-96231b3b80d8