Move PHY_MICREL and PHY_MICREL_KSZ90X1 to Kconfig

Signed-off-by: Alexandru Gagniuc <alex.g@adaptrum.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/configs/nitrogen6s1g_defconfig b/configs/nitrogen6s1g_defconfig
index e458519..26ec663 100644
--- a/configs/nitrogen6s1g_defconfig
+++ b/configs/nitrogen6s1g_defconfig
@@ -34,6 +34,8 @@
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_SST=y
 CONFIG_PHYLIB=y
+CONFIG_PHY_MICREL=y
+CONFIG_PHY_MICREL_KSZ90X1=y
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y
 CONFIG_USB_KEYBOARD=y