xenbus: add module description

Modules without a description now cause a warning:

WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/xen/xenbus/xenbus_probe_frontend.o

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250328113302.2632353-1-arnd@kernel.org>

Author: arndb

drivers/xen/xenbus/xenbus_probe_frontend.c

@@ -513,4 +513,5 @@ static int __init boot_wait_for_devices(void)
 late_initcall(boot_wait_for_devices);
 #endif
 
+MODULE_DESCRIPTION("Xen PV-device frontend support");
 MODULE_LICENSE("GPL");