Revert "net: Have netpoll bring-up DSA management interface"

This reverts commit 1532b977.

The above commit is good and it works, however it was meant as a bugfix
for stable kernels and now we have more self-contained ways in DSA to
handle the situation where the DSA master must be brought up.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>