net: Use netif_threaded_enable instead of netif_set_threaded in drivers

net: Use netif_threaded_enable instead of netif_set_threaded in drivers

Prepare for adding an enum type for NAPI threaded states by adding
netif_threaded_enable API. De-export the existing netif_set_threaded API
and only use it internally. Update existing drivers to use
netif_threaded_enable instead of the de-exported netif_set_threaded.

Note that dev_set_threaded used by mt76 debugfs file is unchanged.

Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
Link: https://patch.msgid.link/20250723013031.2911384-3-skhawaja@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>