[Mips] Remove unused member function argument.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@204352 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Remove the dead code.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@204353 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Join two for loops over defined atoms into the single one.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@204354 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Reduce the number of 'const' casts.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@204355 91177308-0d34-0410-b5e6-96231b3b80d8