generic: ar8216: register the switch from the probe routine

Currently the switch gets registered when an ethernet
driver connects to a PHY of the switch. This method does
not work with the ethernet drivers which are connecting
to the PHY from their ndo_open callback. With those
ethernet drivers, the driver tries to register the switch
each time when the etherned device is opened and this causes
a deadlock.

Move the switch registration into the probe routine to fix
this problem.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35602 3c298f89-4303-0410-b956-a3cf2f4a3e73