[Mips] Exit from the class method as soon as possible.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@202287 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Use a correct number of bits when apply result of calculated relocation.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@202288 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Split reloc26 function into two parts - for processing local and
external relocations.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@202289 91177308-0d34-0410-b5e6-96231b3b80d8