net: ll_temac: fix interrupt bug when interrupt 0 is used

The code is not checking the interrupt for DMA correctly so that an
interrupt number of 0 will cause a false error.

Signed-off-by: Brian Hill <brian.hill@xilinx.com>
Signed-off-by: John Linn <john.linn@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>