[compiler-rt] Enable ASAN for powerpc64le-linux

Whitespace update for lint check by myself (Will).  Otherwise code and comments by Peter Bergner, as previously seen on llvm-commits.

    The following patch gets ASAN somewhat working on powerpc64le-linux.
    It currently assumes the LE kernel uses 46-bit addressing, which is
    true, but it doesn't solve the case for BE where it may be 44 or
    46 bits.  That can be fixed with a follow on patch.

    There are some test suite fails even with this patch that I haven't had
    time to solve yet, but this is better than the state it is in now.
    The limited debugging of those test suite fails seems to show that the
    address map for 46-bit addressing has changed and so we'll need to
    modify the shadow memory location slightly.  Again, that can be fixed
    with a follow on patch.