[LLDB][MIPS] Setting appropriate ArchSpec::m_flags based on ABI

Patch by Nitesh Jain.

Summary: The ArchSpec::m_flags will be set based on ELF flag ABI.

Reviewers: ovyalov, clayborg
Subscribers: lldb-commits, mohit.bhakkad, sagar, jaydeep, bhushan
Differential: D18858
llvm-svn: 269181