Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20180719' into staging

Fix aarch64 host vector mul

# gpg: Signature made Fri 20 Jul 2018 04:58:32 BST
# gpg:                using RSA key 64DF38E8AF7E215F
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>"
# Primary key fingerprint: 7A48 1E78 868B 4DB6 A85A  05C0 64DF 38E8 AF7E 215F

* remotes/rth/tags/pull-tcg-20180719:
  tcg/aarch64: limit mul_vec size

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