MAINTAINERS: Add netdev subsystem profile link

The netdev subsystem has had a subsystem process document for a while
now. Link it appropriately in MAINTAINERS with the P: tag.

Cc: Jakub Kicinski <kuba@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -14994,6 +14994,7 @@ M:	Jakub Kicinski <kuba@kernel.org>
 M:	Paolo Abeni <pabeni@redhat.com>
 L:	netdev@vger.kernel.org
 S:	Maintained
+P:	Documentation/process/maintainer-netdev.rst
 Q:	https://patchwork.kernel.org/project/netdevbpf/list/
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
@@ -15045,6 +15046,7 @@ M:	Jakub Kicinski <kuba@kernel.org>
 M:	Paolo Abeni <pabeni@redhat.com>
 L:	netdev@vger.kernel.org
 S:	Maintained
+P:	Documentation/process/maintainer-netdev.rst
 Q:	https://patchwork.kernel.org/project/netdevbpf/list/
 B:	mailto:netdev@vger.kernel.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git