includes: move openssl headers to include/u-boot

commit 18b06652cd "tools: include u-boot version of sha256.h"
unconditionally forced the sha256.h from u-boot to be used
for tools instead of the host version. This is fragile though
as it will also include the host version. Therefore move it
to include/u-boot to join u-boot/md5.h etc which were renamed
for the same reason.

cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>
diff --git a/lib/sha256.c b/lib/sha256.c
index b1085ea..bb338ba 100644
--- a/lib/sha256.c
+++ b/lib/sha256.c
@@ -13,7 +13,7 @@
 #include <string.h>
 #endif /* USE_HOSTCC */
 #include <watchdog.h>
-#include <sha256.h>
+#include <u-boot/sha256.h>
 
 /*
  * 32-bit integer manipulation macros (big endian)