Convert CONFIG_MACB to Kconfig

This converts the following to Kconfig:
   CONFIG_MACB

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/gurnard_defconfig b/configs/gurnard_defconfig
index 35a2d2e..7c7974c 100644
--- a/configs/gurnard_defconfig
+++ b/configs/gurnard_defconfig
@@ -43,7 +43,7 @@
 # CONFIG_SYS_NAND_USE_FLASH_BBT is not set
 CONFIG_NAND_ATMEL=y
 CONFIG_ATMEL_NAND_HWECC=y
-CONFIG_PHYLIB=y
+CONFIG_MACB=y
 CONFIG_ATMEL_USART=y
 CONFIG_TIMER=y
 CONFIG_ATMEL_PIT_TIMER=y