[llvm-objcopy][ObjectYAML][mips] Add MIPS specific ELF section indexes

This fixes https://github.com/llvm/llvm-project/issues/53998
and displays correct information in obj2yaml for SHN_MIPS_*
sections according to
https://refspecs.linuxfoundation.org/elf/mipsabi.pdf

Reviewed By: jhenderson, MaskRay

Differential Revision: https://reviews.llvm.org/D123902