[ELF][yaml2obj] Handle additional MIPS specific st_other field flags

The ELF symbol `st_other` field might contain additional flags besides
visibility ones. This patch implements support for some MIPS specific
flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221491 91177308-0d34-0410-b5e6-96231b3b80d8