KVM: Introduce struct rtc_status

rtc_status is used to track RTC interrupt delivery status. The pending_eoi
will be increased by vcpu who received RTC interrupt and will be decreased
when EOI to this interrupt.
Also, we use dest_map to record the destination vcpu to avoid the case that
vcpu who didn't get the RTC interupt, but issued EOI with same vector of RTC
and descreased pending_eoi by mistake.

Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>