sh_eth: r8a7790: Handle the RFE (Receive FIFO overflow Error) interrupt

The RFE interrupt is enabled for the r8a7790 but isn't handled,
resulting in the interrupts core noticing unhandled interrupts, and
eventually disabling the ethernet IRQ.

Fix it by adding RFE to the bitmask of error interrupts to be handled
for r8a7790.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>