ar71xx: ag71xx: fix a race involving netdev registration

In particular, phy_connect before register_netdev. This is because
register_netdev runs the netdev notifiers, which can race with the rest of
the initialization in ag71xx_probe. In my case this manifested in two ways:

1) If ag71xx is compiled as a module and inserted after netifd has started,
   netifd is notified by register_netdev before the call to
   ag71xx_phy_connect. netifd tries to bring the interface up, which calls
   ag71xx_open, which in turn enters ag71xx_phy_start. This keys off
   ag->phy_dev (which is still NULL) and thinks this is a fixed-link board,
   and enters ag71xx_link_adjust. This looks at ag->speed which is not yet
   initialized and hits the BUG() in the switch (ag->speed) in
   ag71xx_link_adjust.

   This is the wrong code path for ag71xx_phy_start - my board has PHYs that
   need to be brought up with phy_start. Doing ag71xx_phy_connect before
   register_netdev ensures that ag->phy_dev is non-NULL before
   ag71xx_phy_start is ever called.

2) When ag71xx is built into the kernel, and netconsole is enabled, there
   is a gap in the initial burst of replayed printks right after the netdev
   comes up. My assumption is that netconsole is also triggered by a netdev
   notifier, and part of this printk burst happens before the call into
   ag71xx_phy_connect, so part of the burst is lost while the PHY comes up.
   This patch fixes the gap - all the printks before eth0 comes up are bursted
   in full when netconsole initializes.

ag71xx_phy_connect_xxx no longer runs with a registered netdev, so the
logging has been adjusted accordingly to avoid "unregistered net_device" or
"eth%d" messages in dmesg.

Signed-off-by: Catalin Patulea <cat@vv.carleton.ca>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38689 3c298f89-4303-0410-b956-a3cf2f4a3e73