usb: gadget: avoid unusual inline assembly

clang does not understand the "mrc%?" syntax:

drivers/usb/gadget/udc/pxa25x_udc.c:2330:11: error: invalid % escape in inline assembly string

I don't understand it either, but removing the %? here gets it to build.
This is probably wrong and someone else should do a proper patch.

Any suggestions?
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20210927123830.1278953-1-arnd@kernel.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/pxa25x_udc.c

@@ -2325,7 +2325,7 @@ static int pxa25x_udc_probe(struct platform_device *pdev)
 	pr_info("%s: version %s\n", driver_name, DRIVER_VERSION);
 
 	/* insist on Intel/ARM/XScale */
-	asm("mrc%? p15, 0, %0, c0, c0" : "=r" (chiprev));
+	asm("mrc p15, 0, %0, c0, c0" : "=r" (chiprev));
 	if ((chiprev & CP15R0_VENDOR_MASK) != CP15R0_XSCALE_VALUE) {
 		pr_err("%s: not XScale!\n", driver_name);
 		return -ENODEV;