gianfar: fix coalescing setup in ethtool support

Parameter order for using mk_ic_value(count, time) was reversed,
the patch fixes this.

Signed-off-by: Jiajun Wu <b06378@freescale.com>
Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>