TDLS: Work around interop issues with supported operating class

TDLS: Work around interop issues with supported operating class

It looks like some deployed devices may send an invalid supported
operating class element (length = 0) in TDLS Setup messages. With
cfg80211, this results in the NL80211_CMD_SET_STATION command failing
due to an invalid argument (cfg80211 mandates supported operating
classes information to have a length of 2..253 octets).

Work around this interop issue by ignoring the Supported Operating Class
element if it has invalid length.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>