[ELF][MIPS] Separate calculation of MIPS GOT index and offset of the corresponding part of the GOT. NFC
[ELF][MIPS] Separate calculation of MIPS GOT index and offset of the corresponding part of the GOT. NFC

MIPS GOT consists of some parts: local, global, TLS entries. This change
separates calculation of MIPS GOT index and offset of the corresponding
part of the GOT. That makes code a bit clear and allow to extend number
of parts in the future.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@284750 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld