staging: rtl8192u: Fix typo in comment

Fix the typo "cheked" -> "checked" in comment

Signed-off-by: Xianting Tian <xianting_tian@126.com>
Link: https://lore.kernel.org/r/1573306614-21490-1-git-send-email-xianting_tian@126.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>