Kconfig: define MD5 dependency for FIT support

FIT images require MD5 support to verify image checksums. So far this
was expressed by defining a CPP symbol in image.h. Since MD5 is now a
first class Kconfig citizen, express that in Kconfig instead.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/Kconfig b/Kconfig
index 81b4226..e0744d1 100644
--- a/Kconfig
+++ b/Kconfig
@@ -144,6 +144,7 @@
 
 config FIT
 	bool "Support Flattened Image Tree"
+	select MD5
 	help
 	  This option allows you to boot the new uImage structure,
 	  Flattened Image Tree.  FIT is formally a FDT, which can include
diff --git a/include/image.h b/include/image.h
index 1e686b7..2372518 100644
--- a/include/image.h
+++ b/include/image.h
@@ -67,7 +67,6 @@
 #  endif
 # else
 #  define CONFIG_CRC32		/* FIT images need CRC32 support */
-#  define CONFIG_MD5		/* and MD5 */
 #  define CONFIG_SHA1		/* and SHA1 */
 #  define CONFIG_SHA256		/* and SHA256 */
 #  define IMAGE_ENABLE_CRC32	1