Remove \brief commands from doxygen comments.

We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.

Patch produced by

  for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done

Differential Revision: https://reviews.llvm.org/D46290

llvm-svn: 331272
diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 11b814e..7345591 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -414,7 +414,7 @@
       return Subtarget->getInstrInfo();
     }
 
-    /// \brief Address-mode matching performs shift-of-and to and-of-shift
+    /// Address-mode matching performs shift-of-and to and-of-shift
     /// reassociation in order to expose more scaled addressing
     /// opportunities.
     bool ComplexPatternFuncMutatesDAG() const override {