Remove @brief commands from doxygen comments, too.

This is a follow-up to r331272.

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

https://reviews.llvm.org/D46290

llvm-svn: 331275
diff --git a/llvm/lib/CodeGen/RegAllocPBQP.cpp b/llvm/lib/CodeGen/RegAllocPBQP.cpp
index 7ce4438..879330a 100644
--- a/llvm/lib/CodeGen/RegAllocPBQP.cpp
+++ b/llvm/lib/CodeGen/RegAllocPBQP.cpp
@@ -188,7 +188,7 @@
 
 char RegAllocPBQP::ID = 0;
 
-/// @brief Set spill costs for each node in the PBQP reg-alloc graph.
+/// Set spill costs for each node in the PBQP reg-alloc graph.
 class SpillCosts : public PBQPRAConstraint {
 public:
   void apply(PBQPRAGraph &G) override {
@@ -212,7 +212,7 @@
   }
 };
 
-/// @brief Add interference edges between overlapping vregs.
+/// Add interference edges between overlapping vregs.
 class Interference : public PBQPRAConstraint {
 private:
   using AllowedRegVecPtr = const PBQP::RegAlloc::AllowedRegVector *;