drivers:rtl8192u:remove the use of obsolete create_workqueue in r8192U_core.c

Remove the use of obsolete create_workqueue(name, 0) interface
in r8192U_core.c, since it has changed.

Signed-off-by: Wanlong Gao <wanlong.gao@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>