KVM: SVM: Don't check for assigned device(s) when activating AVIC

KVM: SVM: Don't check for assigned device(s) when activating AVIC

Don't short-circuit IRTE updating when (de)activating AVIC based on the
VM having assigned devices, as nothing prevents AVIC (de)activation from
racing with device (de)assignment.  And from a performance perspective,
bailing early when there is no assigned device doesn't add much, as
ir_list_lock will never be contended if there's no assigned device.

Link: https://lore.kernel.org/r/20250611224604.313496-47-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>