xhcid: promote IRQ reactor startup lines to info level

'Running IRQ reactor with IRQ file and event queue' and 'in polling
mode' were debug! since the file was created, so test-xhci-irq-qemu.sh
(which greps for the interrupt-driven line) could never see them at the
default info log level — the IRQ-driven path had zero runtime evidence.
They are one-time startup lines; promote to info so the interrupt
delivery mode is observable and the proof can detect it.

drivers/usb/xhcid/src/xhci/irq_reactor.rs

@@ -128,7 +128,7 @@ impl<const N: usize> IrqReactor<N> {
         std::thread::sleep(std::time::Duration::from_millis(2));
     }
     fn run_polling(mut self) -> ! {
-        debug!("Running IRQ reactor in polling mode.");
+        log::info!("Running IRQ reactor in polling mode.");
         let hci_clone = Arc::clone(&self.hci);
 
         let mut event_trb_index = {
@@ -180,7 +180,7 @@ impl<const N: usize> IrqReactor<N> {
     }
 
     fn run_with_irq_file(mut self) -> ! {
-        debug!("Running IRQ reactor with IRQ file and event queue");
+        log::info!("Running IRQ reactor with IRQ file and event queue");
 
         let hci_clone = Arc::clone(&self.hci);
         let event_queue =