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_defconfig b/configs/ls2080ardb_defconfig
index 4840304..be06206 100644
--- a/configs/ls2080ardb_defconfig
+++ b/configs/ls2080ardb_defconfig
@@ -45,6 +45,7 @@
 CONFIG_DM_SPI_FLASH=y
 CONFIG_PHYLIB=y
 CONFIG_PHY_AQUANTIA=y
+CONFIG_PHY_CORTINA=y
 CONFIG_E1000=y
 CONFIG_MII=y
 CONFIG_PCI=y