bootutil/includes/enc_key: move public part to enc_key_public.h

Part of defines which are needed for bootutil_public.c compilation
were moved to separate file, so the bootutil_public library doesn't
need to include cryptographic libraries headers anymore.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/bootutil/src/bootutil_public.c b/boot/bootutil/src/bootutil_public.c
index 9891aea..5afe305 100644
--- a/boot/bootutil/src/bootutil_public.c
+++ b/boot/bootutil/src/bootutil_public.c
@@ -47,7 +47,7 @@
 #include "bootutil/bootutil_public.h"
 #include "bootutil/bootutil_log.h"
 #ifdef MCUBOOT_ENC_IMAGES
-#include "bootutil/enc_key.h"
+#include "bootutil/enc_key_public.h"
 #endif
 
 #ifdef CONFIG_MCUBOOT