usb: sl811-hcd: only defined function checkdone if QUIRK2 is defined

Function checkdone is only required if QUIRK2 is defined, so add
appropriate #if / #endif around the function.

Cleans up clang scan build warning:
drivers/usb/host/sl811-hcd.c:588:18: warning: unused function
'checkdone' [-Wunused-function]
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20240307111351.1982382-1-colin.i.king@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/sl811-hcd.c

@@ -585,6 +585,7 @@ done(struct sl811 *sl811, struct sl811h_ep *ep, u8 bank)
 		finish_request(sl811, ep, urb, urbstat);
 }
 
+#ifdef QUIRK2
 static inline u8 checkdone(struct sl811 *sl811)
 {
 	u8	ctl;
@@ -616,6 +617,7 @@ static inline u8 checkdone(struct sl811 *sl811)
 #endif
 	return irqstat;
 }
+#endif
 
 static irqreturn_t sl811h_irq(struct usb_hcd *hcd)
 {