FIT: Rename FIT_DISABLE_SHA256 to FIT_ENABLE_SHA256_SUPPORT

We rename CONFIG_FIT_DISABLE_SHA256 to CONFIG_FIT_ENABLE_SHA256_SUPPORT which
is enabled by default and now a positive option.  Convert the handful of boards
that were disabling it before to save space.

Cc: Dirk Eibach <eibach@gdsys.de>
Cc: Lukasz Dalek <luk0104@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/h2200_defconfig b/configs/h2200_defconfig
index b85ed59..9d3698c 100644
--- a/configs/h2200_defconfig
+++ b/configs/h2200_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_TARGET_H2200=y
 CONFIG_FIT=y
+# CONFIG_FIT_ENABLE_SHA256_SUPPORT is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set