Merge remote-tracking branch 'remotes/cohuck/tags/kvm_cap_helpers' into staging

Add helpers for enabling kvm capabilities and convert the existing
s390x and ppc users to use them.

# gpg: Signature made Wed 30 Apr 2014 14:48:45 BST using RSA key ID C6F02FAF
# gpg: Can't check signature: public key not found

* remotes/cohuck/tags/kvm_cap_helpers:
  ppc: use kvm_vcpu_enable_cap()
  s390x: use kvm_vcpu_enable_cap()
  kvm: add kvm_{vm,vcpu}_enable_cap

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