fit: make sha256 support optional

sha256 has some beefy memory footprint.
Make it optional for constrained systems.

Signed-off-by: Dirk Eibach <dirk.eibach@gdsys.cc>
diff --git a/include/configs/dlvision-10g.h b/include/configs/dlvision-10g.h
index 2567a22..6153a40 100644
--- a/include/configs/dlvision-10g.h
+++ b/include/configs/dlvision-10g.h
@@ -40,6 +40,7 @@
 /* new uImage format support */
 #define CONFIG_FIT
 #define CONFIG_FIT_VERBOSE	/* enable fit_format_{error,warning}() */
+#define CONFIG_FIT_DISABLE_SHA256
 
 #define CONFIG_ENV_IS_IN_FLASH	/* use FLASH for environment vars */
 
diff --git a/include/configs/io.h b/include/configs/io.h
index 649c0fb..8e32c25 100644
--- a/include/configs/io.h
+++ b/include/configs/io.h
@@ -40,6 +40,7 @@
 /* new uImage format support */
 #define CONFIG_FIT
 #define CONFIG_FIT_VERBOSE	/* enable fit_format_{error,warning}() */
+#define CONFIG_FIT_DISABLE_SHA256
 
 #define CONFIG_ENV_IS_IN_FLASH	/* use FLASH for environment vars */
 
diff --git a/include/configs/iocon.h b/include/configs/iocon.h
index 35ba1bd..ae05bcb 100644
--- a/include/configs/iocon.h
+++ b/include/configs/iocon.h
@@ -39,6 +39,7 @@
 /* new uImage format support */
 #define CONFIG_FIT
 #define CONFIG_FIT_VERBOSE	/* enable fit_format_{error,warning}() */
+#define CONFIG_FIT_DISABLE_SHA256
 
 #define CONFIG_ENV_IS_IN_FLASH	/* use FLASH for environment vars */
 
diff --git a/include/configs/neo.h b/include/configs/neo.h
index 75dc862..4937730 100644
--- a/include/configs/neo.h
+++ b/include/configs/neo.h
@@ -37,6 +37,7 @@
 /* new uImage format support */
 #define CONFIG_FIT
 #define CONFIG_FIT_VERBOSE	/* enable fit_format_{error,warning}() */
+#define CONFIG_FIT_DISABLE_SHA256
 
 #define CONFIG_ENV_IS_IN_FLASH	/* use FLASH for environment vars */