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/axm_defconfig b/configs/axm_defconfig
index b0e69e1..b99ddb9 100644
--- a/configs/axm_defconfig
+++ b/configs/axm_defconfig
@@ -37,4 +37,5 @@
 # CONFIG_MMC is not set
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_STMICRO=y
+CONFIG_PHYLIB=y
 CONFIG_USE_TINY_PRINTF=y