nan: Update NMI when MAC address changes

The NAN Management Interface (NMI) address in the NAN Discovery Engine
(nan_de) was only set during initialization. This address would become
stale if the interface's MAC address changed later, for example, due to
MAC address randomization.

When `wpa_supplicant_update_mac_addr()` updated `wpa_s->own_addr`, the
corresponding `wpa_s->nan_de->nmi` field was not updated. This could
lead to failures in Wi-Fi Aware USD operations as they would be using
an incorrect source MAC address.

This commit fixes this by:
1. Introducing a new function, `nan_de_update_nmi()`, to allow the NMI
   to be updated after initialization.
2. Calling this new function from `wpa_supplicant_update_mac_addr()` to
   ensure the NMI is always synchronized with the interface's current
   MAC address.

This ensures the NAN Discovery Engine operates with the correct MAC
address, improving the reliability of Wi-Fi Aware USD functionality.

Bug: 421452165
Test: Manual - USD Transmit message
Change-Id: I57323f63a3680b337db41de677058328ce17406e
3 files changed