net: rtlwifi: properly check for alloc_workqueue() failure

If alloc_workqueue() fails, properly catch this and propagate the error
to the calling functions, so that the devuce initialization will
properly error out.

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Bryan Brattlof <hello@bryanbrattlof.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210503115736.2104747-14-gregkh@linuxfoundation.org


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