[AVR] Don't look for the TargetFrameLowering in the FrameLowering implementation

c.f. r364349

llvm-svn: 364632
diff --git a/llvm/lib/Target/AVR/AVRFrameLowering.cpp b/llvm/lib/Target/AVR/AVRFrameLowering.cpp
index b1b1fd1..5e91bb8 100644
--- a/llvm/lib/Target/AVR/AVRFrameLowering.cpp
+++ b/llvm/lib/Target/AVR/AVRFrameLowering.cpp
@@ -380,7 +380,7 @@
   // For adjcallstackdown we convert it into an 'adiw reg, <amt>' handling
   // the read and write of SP in I/O space.
   if (Amount != 0) {
-    assert(TFI.getStackAlignment() == 1 && "Unsupported stack alignment");
+    assert(getStackAlignment() == 1 && "Unsupported stack alignment");
 
     if (Opcode == TII.getCallFrameSetupOpcode()) {
       fixStackStores(MBB, MI, TII, true);