NCG: Fix Typo in Register Allocator Loop Patch

Fix previous patch "NCG: Handle loops in register allocator"
Of course, I broke it when correcting a style problem just before committing.

ghc/compiler/nativeGen/RegisterAlloc.hs

@@ -341,7 +341,7 @@ computeLiveness sccs
 
 
               linearLiveness :: BlockMap RegSet -> [NatBasicBlock]
-                             -> (BlockMap RegSet, AnnBasicBlock])
+                             -> (BlockMap RegSet, [AnnBasicBlock])
               linearLiveness = mapAccumL processBlock
 
 	      processBlock blockmap input@(BasicBlock block_id instrs)