Convert CONFIG_CMD_BLOB to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_BLOB

Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: Add imply CMD_BLOB under CHAIN_OF_TRUST]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/freescale/common/Kconfig b/board/freescale/common/Kconfig
index f5190ac..8a9a9be 100644
--- a/board/freescale/common/Kconfig
+++ b/board/freescale/common/Kconfig
@@ -1,5 +1,6 @@
 config CHAIN_OF_TRUST
 	depends on !FIT_SIGNATURE && SECURE_BOOT
+	imply CMD_BLOB
 	select FSL_CAAM
 	bool
 	default y