wifi: Add a new feature capability to indicate multiple MLD supported

When device didn't support multiple MLD, the framework will use
1 MLD only for all use case. (For example: no bridged sinal link AP
dual APs(tethered + LOHS).
Note: But MLO AP is allowed since MLO SoftAp only need 1 MLD.

Bug: 382023801
Test: TH
Change-Id: Id89e6f10c042445e8c85274b8250677cde315a9e