net: s/dev_get_mac_address/netif_get_mac_address/

net: s/dev_get_mac_address/netif_get_mac_address/

Commit cc34acd577f1 ("docs: net: document new locking reality")
introduced netif_ vs dev_ function semantics: the former expects locked
netdev, the latter takes care of the locking. We don't strictly
follow this semantics on either side, but there are more dev_xxx handlers
now that don't fit. Rename them to netif_xxx where appropriate.

netif_get_mac_address is used only by tun/tap, so move it into
NETDEV_INTERNAL namespace.

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250717172333.1288349-3-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>