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/AMDGPU/SIDebuggerInsertNops.cpp b/llvm/lib/Target/AMDGPU/SIDebuggerInsertNops.cpp
index b5c439b..69ec381 100644
--- a/llvm/lib/Target/AMDGPU/SIDebuggerInsertNops.cpp
+++ b/llvm/lib/Target/AMDGPU/SIDebuggerInsertNops.cpp
@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 //
 /// \file
-/// \brief Inserts one nop instruction for each high level source statement for
+/// Inserts one nop instruction for each high level source statement for
 /// debugger usage.
 ///
 /// Tools, such as a debugger, need to pause execution based on user input (i.e.