ELF: Set e_flags header only when MIPS.
ELF: Set e_flags header only when MIPS.

The field is zero by default, so this is NFC.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@263385 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld