Merge remote-tracking branch 'remotes/rth/tags/pull-tile-20151030' into staging

Prefetch in y2 pipe

# gpg: Signature made Fri 30 Oct 2015 20:40:02 GMT using RSA key ID 4DD0279B
# gpg: Good signature from "Richard Henderson <rth7680@gmail.com>"
# gpg:                 aka "Richard Henderson <rth@redhat.com>"
# gpg:                 aka "Richard Henderson <rth@twiddle.net>"

* remotes/rth/tags/pull-tile-20151030:
  target-tilegx: Implement prefetch instructions in pipe y2

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>