[Mips] Remove unused class member declaration.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@209591 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Factor out the code create Mips specific runtime file into
the MipsELFWriters member function.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@209592 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Factor out the code assign a value to the absolute atom into the
separate function.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@209593 91177308-0d34-0410-b5e6-96231b3b80d8