[MIPS] Avoid breakpoint in delay slot

    
    SUMMARY:
    This patch implements Target::GetBreakableLoadAddress() method that takes an address
    and checks for any reason there is a better address than this to put a breakpoint on.
    If there is then return that address.
    MIPS uses this method to avoid breakpoint in delay slot.
    
    Reviewers: clayborg, jingham
    Subscribers: jingham, mohit.bhakkad, sagar, jaydeep, nitesh.jain, lldb-commits
    Differential Revision: http://http://reviews.llvm.org/D12184

llvm-svn: 246015