net: add ICPlus PHY driver

The driver code was taken from Linux kernel source:
drivers/net/phy/icplus.c

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 8f4c0c6..77d19c6 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -433,6 +433,9 @@
 #ifdef CONFIG_PHY_ET1011C
 	phy_et1011c_init();
 #endif
+#ifdef CONFIG_PHY_ICPLUS
+	phy_icplus_init();
+#endif
 #ifdef CONFIG_PHY_LXT
 	phy_lxt_init();
 #endif