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/octeontx_81xx_defconfig b/configs/octeontx_81xx_defconfig
index 6e6a8d6..706cc41 100644
--- a/configs/octeontx_81xx_defconfig
+++ b/configs/octeontx_81xx_defconfig
@@ -82,6 +82,7 @@
 CONFIG_AHCI_PCI=y
 CONFIG_DM_I2C=y
 CONFIG_MISC=y
+CONFIG_SUPPORT_EMMC_BOOT=y
 CONFIG_MMC_OCTEONTX=y
 CONFIG_MTD=y
 CONFIG_DM_SPI_FLASH=y