linux: enable CONFIG_AUDIT if the audit package is selected

linux: enable CONFIG_AUDIT if the audit package is selected

We already turn on kernel features for several packages, so let's do it
for audit too, since the daemon is useless and fails to load otherwise.

Notice that we also turn NET on, since AUDIT depends on NET, like we do
for the wireguard package.

Signed-off-by: Carlos Santos <casantos@datacom.com.br>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>