Convert CONFIG_SUPPORT_EMMC_BOOT to Kconfig

This converts the following to Kconfig:
	CONFIG_SUPPORT_EMMC_BOOT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/variscite_dart6ul_defconfig b/configs/variscite_dart6ul_defconfig
index b53169d..53a49cc 100644
--- a/configs/variscite_dart6ul_defconfig
+++ b/configs/variscite_dart6ul_defconfig
@@ -37,6 +37,7 @@
 CONFIG_SYS_I2C_MXC=y
 CONFIG_MISC=y
 CONFIG_I2C_EEPROM=y
+CONFIG_SUPPORT_EMMC_BOOT=y
 CONFIG_FSL_USDHC=y
 CONFIG_MTD=y
 CONFIG_PHYLIB=y