staging: rtl8188eu: Fix module loading from tasklet for WEP encryption

Commit 2b2ea09e ("staging:r8188eu: Use lib80211 to decrypt WEP-frames")
causes scheduling while atomic bugs followed by a hard freeze whenever
the driver tries to connect to a WEP-encrypted network. Experimentation
showed that the freezes were eliminated when module lib80211 was
preloaded, which can be forced by calling lib80211_get_crypto_ops()
directly rather than indirectly through try_then_request_module().
With this change, no BUG messages are logged.

Fixes: 2b2ea09e ("staging:r8188eu: Use lib80211 to decrypt WEP-frames")
Cc: Stable <stable@vger.kernel.org> # v4.17+
Cc: Michael Straube <straube.linux@gmail.com>
Cc: Ivan Safonov <insafonov@gmail.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>