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/Hexagon/HexagonGatherPacketize.cpp b/llvm/lib/Target/Hexagon/HexagonGatherPacketize.cpp
index dcffec7..253f09d 100644
--- a/llvm/lib/Target/Hexagon/HexagonGatherPacketize.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonGatherPacketize.cpp
@@ -13,6 +13,7 @@
 
 #include "HexagonTargetMachine.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBundle.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 using namespace llvm;