gianfar: Merge Tx and Rx interrupt for scheduling clean up ring

No clean up function is executed in the interrupt context by this patch.

Signed-off-by: Dai Haruki <dai.haruki@freescale.com>
Acked-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>