xen/events: remove unnecessary init_evtchn_cpu_bindings()

Because the guest-side binding of an event to a VCPU (i.e., setting
the local per-cpu masks) is always explicitly done after an event
channel is bound to a port, there is no need to initialize all
possible events as bound to VCPU 0 at start of day or after a resume.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>