Merge remote-tracking branch 'remotes/ehabkost/tags/x86-pull-request' into staging

X86 fixes, 2015-11-17

Two X86 fixes, hopefully in time for -rc1.

# gpg: Signature made Tue 17 Nov 2015 19:06:53 GMT using RSA key ID 984DC5A6
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>"

* remotes/ehabkost/tags/x86-pull-request:
  target-i386: Disable rdtscp on Opteron_G* CPU models
  target-i386: Fix mulx for identical target regs

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