Convert CONFIG_FEC_MXC to Kconfig

This converts the following to Kconfig:
	CONFIG_FEC_MXC

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/pico-imx8mq_defconfig b/configs/pico-imx8mq_defconfig
index 9ac7656..e63b119 100644
--- a/configs/pico-imx8mq_defconfig
+++ b/configs/pico-imx8mq_defconfig
@@ -50,6 +50,7 @@
 CONFIG_SUPPORT_EMMC_BOOT=y
 CONFIG_FSL_USDHC=y
 CONFIG_DM_ETH=y
+CONFIG_FEC_MXC=y
 CONFIG_PINCTRL=y
 CONFIG_PINCTRL_IMX8M=y
 CONFIG_SPL_POWER_LEGACY=y