[PowerPC] Swap arguments to vpkuhum/vpkuwum on little-endian

In commit r213915, Bill fixed little-endian usage of vmrgh* and vmrgl*
by swapping the input arguments.  As it turns out, the exact same fix
is also required for the vpkuhum/vpkuwum patterns.

This fixes another regression in llvmpipe when vector support is
enabled.

Reviewed by Bill Schmidt.

llvm-svn: 214718
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index b8b917e..b4f8550 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -301,12 +301,12 @@
   namespace PPC {
     /// isVPKUHUMShuffleMask - Return true if this is the shuffle mask for a
     /// VPKUHUM instruction.
-    bool isVPKUHUMShuffleMask(ShuffleVectorSDNode *N, bool isUnary,
+    bool isVPKUHUMShuffleMask(ShuffleVectorSDNode *N, unsigned ShuffleKind,
                               SelectionDAG &DAG);
 
     /// isVPKUWUMShuffleMask - Return true if this is the shuffle mask for a
     /// VPKUWUM instruction.
-    bool isVPKUWUMShuffleMask(ShuffleVectorSDNode *N, bool isUnary,
+    bool isVPKUWUMShuffleMask(ShuffleVectorSDNode *N, unsigned ShuffleKind,
                               SelectionDAG &DAG);
 
     /// isVMRGLShuffleMask - Return true if this is a shuffle mask suitable for