KVM: correct null pid check in kvm_vcpu_yield_to()

Correct a simple mistake of checking the wrong variable
before a dereference, resulting in the dereference not being
properly protected by rcu_dereference().

Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 27fbe64bfa63cfb9da025975b59d96568caa2d53)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
1 file changed