KVM: arm64: get rid of var ret and out jump label in kvm_arch_vcpu_ioctl_set_guest_debug()

I don't think there is anything wrong with the existing code.
It may not be to your own taste, but is in keeping with a lot of the KVM code.

If you were making changes to this code, I wouldn't object. But on its own, this is just churn.

Thanks,

         M.