xhcid/irq_reactor: take trb by mut value in acknowledge fns (fix E0596)

acknowledge() and acknowledge_failed_transfer_trbs() call trb.reserved(false)
(a &mut self method) on a by-value `trb: Trb` parameter that wasn't declared
mut. Bind it `mut trb: Trb` (the parameter is owned, so this is sufficient).
Fixes the 2 E0596 errors that failed `cook base`; the 49 warnings are non-fatal.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -435,7 +435,7 @@ impl<const N: usize> IrqReactor<N> {
                 .inspect(|req| trace!("Received request: {:X?}", req)),
         );
     }
-    fn acknowledge(&mut self, trb: Trb) {
+    fn acknowledge(&mut self, mut trb: Trb) {
         //TODO: handle TRBs without an attached state
 
         trace!("ACK TRB {:X?}", trb);
@@ -565,7 +565,7 @@ impl<const N: usize> IrqReactor<N> {
             trb
         );
     }
-    fn acknowledge_failed_transfer_trbs(&mut self, trb: Trb) {
+    fn acknowledge_failed_transfer_trbs(&mut self, mut trb: Trb) {
         let mut index = 0;
 
         loop {