Convert CONFIG_PHY_CORTINA to Kconfig

This converts the following to Kconfig:
   CONFIG_PHY_CORTINA

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ls2080ardb_nand_defconfig b/configs/ls2080ardb_nand_defconfig
index 49bdd58..bd5a953 100644
--- a/configs/ls2080ardb_nand_defconfig
+++ b/configs/ls2080ardb_nand_defconfig
@@ -54,6 +54,7 @@
 CONFIG_SYS_FLASH_CFI=y
 CONFIG_PHYLIB=y
 CONFIG_PHY_AQUANTIA=y
+CONFIG_PHY_CORTINA=y
 CONFIG_E1000=y
 CONFIG_MII=y
 CONFIG_PCI=y