Generate TBZ/TBNZ for certain comparisons against zero. E.g. instead of:

    cmp w0, 0x0
    b.lt/ge <addr>

we can generate:

    tbnz/tbz w0, 31, <addr>

BUG=

Review-Url: https://codereview.chromium.org/2359723004
Cr-Commit-Position: refs/heads/master@{#39620}