The IP101A_G_IRQ_CONF_STATUS register has bits to detect which
interrupts have fired. Implement the .did_interrupt callback to let the
PHY core know whether the interrupt was for this specific PHY.

This is useful for debugging interrupt problems with 32-pin IP101GR PHYs
where the interrupt line is shared with the RX_ERR (receive error
status) signal. The default values are:
- RX_ERR is enabled by default (LOW means that there is no receive
  error)
- the PHY's interrupt line is configured "active low" by default

Without any additional changes there is a flood of interrupts if the
RX_ERR/INTR32 signal is configured in RX_ERR mode (which is the
default). Having a did_interrupt ensures that the PHY core returns
IRQ_NONE instead of endlessly triggering the PHY state machine.
Additionally the kernel will report this after a while:
  irq 28: nobody cared (try booting with the "irqpoll" option)
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>