Rename LiveIntervalAnalysis.h to LiveIntervals.h

Headers/Implementation files should be named after the class they
declare/define.

Also eliminated an `#include "llvm/CodeGen/LiveIntervalAnalysis.h"` in
favor of `class LiveIntarvals;`

llvm-svn: 320546
diff --git a/llvm/lib/Target/AMDGPU/SIFixWWMLiveness.cpp b/llvm/lib/Target/AMDGPU/SIFixWWMLiveness.cpp
index 3f657b9..3493c77 100644
--- a/llvm/lib/Target/AMDGPU/SIFixWWMLiveness.cpp
+++ b/llvm/lib/Target/AMDGPU/SIFixWWMLiveness.cpp
@@ -57,7 +57,7 @@
 #include "SIRegisterInfo.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/SparseBitVector.h"
-#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "llvm/CodeGen/LiveIntervals.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"