net: marvell: prestera: move netdev topology validation to prestera_main

Move handling of PRECHANGEUPPER event from prestera_switchdev to
prestera_main which is responsible for basic netdev events handling
and routing them to related module.

Signed-off-by: Vadym Kochan <vkochan@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>