xhci: Don't require a valid get_quirks() function pointer during xhci setup

Not all platforms drivers need to set up custom quirks during the xhci
generic setup. Allow them to pass NULL as the function pointer when
calling xhci_gen_setup()
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Message-ID: <20230602144009.1225632-4-mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci.c

@@ -5181,7 +5181,8 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
 
 	xhci->quirks |= quirks;
 
-	get_quirks(dev, xhci);
+	if (get_quirks)
+		get_quirks(dev, xhci);
 
 	/* In xhci controllers which follow xhci 1.0 spec gives a spurious
 	 * success event after a short transfer. This quirk will ignore such