Use getError instead of the error_code operator.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@198797 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Remove unnecessary #include pragma.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@198798 91177308-0d34-0410-b5e6-96231b3b80d8