net: dsa: Rename DSA probe function.

Rename the function called from the DSA to perform a probe for the
switch. This makes the normal _probe() name available for a standard
Linux device driver probe function.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>