[AVR] Save/restore the frame pointer for all functions

A recent commit I made made it so that we only did this for signal or
interrupt handlers. This broke normal functions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301893 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed