net80211: proper ssid length check in setmlme_assoc_adhoc()

A user supplied SSID length is used without proper checks in
setmlme_assoc_adhoc() which can lead to copies beyond the end
of the user supplied buffer.
The ssid is a fixed size array for the ioctl and the argument
to setmlme_assoc_adhoc().
In addition to an ssid_len check of 0 also error in case the
ssid_len is larger than the size of the ssid array to prevent
problems.

PR: 254737
Reported by: Tommaso (cutesmilee.research protonmail.com)

(cherry picked from commit 526370fb85db4b659cff4625eb2f379acaa4a1a8)
(cherry picked from commit 0525ece3554edce14fa68a7fb61078ae2110c44b)