[AVR] Remove unneeded XFAILs from the Generic CodeGen tests

These have been in place for quite a while now.

Several bugs have since been fixed, and these tests now pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351679 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed