staging: wfx: check ssidlen and prevent an array overflow

We need to cap "ssidlen" to prevent a memcpy() overflow.

Fixes: 40115bbc ("staging: wfx: implement the rest of mac80211 API")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200424104235.GA416402@mwanda


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