wifi: mac80211: Update MCS15 support in link_conf

wifi: mac80211: Update MCS15 support in link_conf

As per IEEE 802.11be-2024 - 9.4.2.321, EHT operation element
contains MCS15 Disable subfield as the sixth bit, which is set when
MCS15 support is not enabled.

Get MCS15 support from EHT operation params and add it in link_conf
so that driver can use this value to know if EHT-MCS 15 reception
is enabled.

Co-developed-by: Dhanavandhana Kannan <quic_dhanavan1@quicinc.com>
Signed-off-by: Dhanavandhana Kannan <quic_dhanavan1@quicinc.com>
Signed-off-by: Mohan Kumar G <quic_mkumarg@quicinc.com>
Link: https://patch.msgid.link/20250505152836.3266829-1-quic_mkumarg@quicinc.com
[remove pointless !! for bool assignment]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>