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/bcm_ns3_defconfig b/configs/bcm_ns3_defconfig
index 6b7f42f..1305434 100644
--- a/configs/bcm_ns3_defconfig
+++ b/configs/bcm_ns3_defconfig
@@ -36,6 +36,7 @@
 CONFIG_DM=y
 CONFIG_CLK=y
 CONFIG_CLK_CCF=y
+CONFIG_SUPPORT_EMMC_BOOT=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_SDMA=y
 CONFIG_MMC_SDHCI_IPROC=y