Move PHYLIB to Kconfig

Signed-off-by: Alexandru Gagniuc <alex.g@adaptrum.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/configs/silk_defconfig b/configs/silk_defconfig
index d2d20b9..d7d6111 100644
--- a/configs/silk_defconfig
+++ b/configs/silk_defconfig
@@ -24,6 +24,7 @@
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_BAR=y
 CONFIG_SPI_FLASH_SPANSION=y
+CONFIG_PHYLIB=y
 CONFIG_BAUDRATE=38400
 CONFIG_SCIF_CONSOLE=y
 CONFIG_USB=y