net: phy: smsc: simplify config_init callback

Exit the driver specific config_init hook early if energy detection is
disabled. We can do this because we don't need to clear the interrupt
status here. Clearing the status should be removed anyway since this is
handled by the phy_enable_interrupts().

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>