x86/nvmx: only update SVI when using Ack on exit

x86/nvmx: only update SVI when using Ack on exit

Check whether there's a valid interrupt in VM_EXIT_INTR_INFO in order
to decide whether to update SVI in nvmx_update_apicv. If Ack on exit
is not being used VM_EXIT_INTR_INFO won't have a valid interrupt and
hence SVI shouldn't be updated to signal the interrupt is currently in
service because it won't be Acked.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>