usbip: vudc: Make use of the helper macro LIST_HEAD()

Replace "struct list_head head = LIST_HEAD_INIT(head)" with
"LIST_HEAD(head)" to simplify the code.

LIST_HEAD() helps to clean up the code "struct list_head vudc_devices =",
only to care about the variable 'vudc_devices'.
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Cai Huoqing <cai.huoqing@linux.dev>
Link: https://lore.kernel.org/r/20220211012807.7415-1-cai.huoqing@linux.devSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/usbip/vudc_main.c

@@ -26,7 +26,7 @@ static struct platform_driver vudc_driver = {
 	},
 };
 
-static struct list_head vudc_devices = LIST_HEAD_INIT(vudc_devices);
+static LIST_HEAD(vudc_devices);
 
 static int __init init(void)
 {