net: Fix problem with 405EZ ethernet interrupt

On 405EZ the RX-/TX-interrupts are coalesced into one IRQ bit in the
UIC. We need to acknowledge the RX-/TX-interrupts in the
SDR0_ICINTSTAT reg as well.

This problem was introduced with commit
d1631fe1 [ppc4xx: Consolidate PPC4xx UIC defines]

Signed-off-by: James Clough <james@rtetc.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>