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/ls2088ardb_tfa_defconfig b/configs/ls2088ardb_tfa_defconfig
index 1730c9a..ed7ef43 100644
--- a/configs/ls2088ardb_tfa_defconfig
+++ b/configs/ls2088ardb_tfa_defconfig
@@ -59,6 +59,7 @@
 # CONFIG_SPI_FLASH_USE_4K_SECTORS is not set
 CONFIG_PHYLIB=y
 CONFIG_PHY_AQUANTIA=y
+CONFIG_PHY_CORTINA=y
 CONFIG_E1000=y
 CONFIG_MII=y
 CONFIG_PCI=y