net: phy: realtek: Dummy IRQ calls for RTL8366RB

This fixes a regression introduced by
commit 0d2e778e
"net: phy: replace PHY_HAS_INTERRUPT with a check for
config_intr and ack_interrupt".

This assumes that a PHY cannot trigger interrupt unless
it has .config_intr() or .ack_interrupt() implemented.
A later patch makes the code assume both need to be
implemented for interrupts to be present.

But this PHY (which is inside a DSA) will happily
fire interrupts without either callback.

Implement dummy callbacks for .config_intr() and
.ack_interrupt() in the phy header to fix this.

Tested on the RTL8366RB on D-Link DIR-685.

Fixes: 0d2e778e

 ("net: phy: replace PHY_HAS_INTERRUPT with a check for config_intr and ack_interrupt")
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>