net: ag71xx: Fix a potential double free in error handling paths

net: ag71xx: Fix a potential double free in error handling paths

BugLink: https://bugs.launchpad.net/bugs/1956926
[ Upstream commit 1cd5384c88af5b59bf9f3b6c1a151bc14b88c2cd ]

'ndev' is a managed resource allocated with devm_alloc_etherdev(), so there
is no need to call free_netdev() explicitly or there will be a double
free().

Simplify all error handling paths accordingly.

Fixes: d51b6ce441d3 ("net: ethernet: add ag71xx driver")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <p.pisati@gmail.com>