usb/early: remove unused including <linux/version.h>

Fix the following versioncheck warning:

drivers/usb/early/xhci-dbc.c:21:1: unused including <linux/version.h>

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20200421033945.27703-1-yanaijie@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>