target-arm: Check error conditions on kvm_arm_reset_vcpu

When resetting a VCPU we currently call both kvm_arm_vcpu_init() and
write_kvmstate_to_list(), both of which can fail, but we never check the
return value.

The only choice here is to print an error an exit if the calls fail.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1418039630-11773-1-git-send-email-christoffer.dall@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
