fec: Fix KS8721BL_ICSR phy register offset

According to the datasheet the ICSR register is at offset 27, not 22.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: David S. Miller <davem@davemloft.net>