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/tools/llvm-mca/Backend.h b/llvm/tools/llvm-mca/Backend.h
index c21da1f..d294b61 100644
--- a/llvm/tools/llvm-mca/Backend.h
+++ b/llvm/tools/llvm-mca/Backend.h
@@ -26,7 +26,7 @@
 class HWInstructionEvent;
 class HWStallEvent;
 
-/// \brief An out of order backend for a specific subtarget.
+/// An out of order backend for a specific subtarget.
 ///
 /// It emulates an out-of-order execution of instructions. Instructions are
 /// fetched from a MCInst sequence managed by an object of class SourceMgr.