wifi: cfg80211: extend to embed link level statistics in NL message

Currently, statistics is supported at deflink( or one of the links)
level for station. This has problems when applied to multi-link(ML)
connections.

Hence, add changes to support link level statistics to embed NL message
with link related information if valid links are present.

This will be helpful to check the link related statistics during MLO.

The statistics will be embedded into NL message as below:
For non-ML:
cmd->
    NL80211_ATTR_IFINDEX
    NL80211_ATTR_MAC
    NL80211_ATTR_GENERATION
    ....etc
    NL80211_ATTR_STA_INFO | nested
        NL80211_STA_INFO_CONNECTED_TIME,
        NL80211_STA_INFO_STA_FLAGS,
        NL80211_STA_INFO_RX_BYTES,
        NL80211_STA_INFO_TX_BYTES,
        .........etc

For MLO:
cmd ->
    NL80211_ATTR_IFINDEX
    NL80211_ATTR_MAC
    NL80211_ATTR_GENERATION
    .......etc
    NL80211_ATTR_STA_INFO | nested
        NL80211_STA_INFO_CONNECTED_TIME,
        NL80211_STA_INFO_STA_FLAGS,
        ........etc
    NL80211_ATTR_MLO_LINK_ID,
    NL80211_ATTR_MLD_ADDR,
    NL80211_ATTR_MLO_LINKS | nested
        link_id-1 | nested
            NL80211_ATTR_MLO_LINK_ID,
            NL80211_ATTR_MAC,
            NL80211_ATTR_STA_INFO | nested
                NL80211_STA_INFO_RX_BYTES,
                NL80211_STA_INFO_TX_BYTES,
               NL80211_STA_INFO_CONNECTED_TIME,
               ..........etc.
        link_id-2 | nested
            NL80211_ATTR_MLO_LINK_ID,
            NL80211_ATTR_MAC,
            NL80211_ATTR_STA_INFO | nested
                NL80211_STA_INFO_RX_BYTES,
                NL80211_STA_INFO_TX_BYTES,
               NL80211_STA_INFO_CONNECTED_TIME,
                .........etc

Signed-off-by: Sarika Sharma <quic_sarishar@quicinc.com>
Link: https://patch.msgid.link/20250528054420.3050133-4-quic_sarishar@quicinc.com


Signed-off-by: Johannes Berg <johannes.berg@intel.com>