boot: mynewt: add config for ECIES-P256 encrypted images

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/boot/mynewt/mcuboot_config/include/mcuboot_config/mcuboot_config.h b/boot/mynewt/mcuboot_config/include/mcuboot_config/mcuboot_config.h
index 13c31fd..889fcdd 100644
--- a/boot/mynewt/mcuboot_config/include/mcuboot_config/mcuboot_config.h
+++ b/boot/mynewt/mcuboot_config/include/mcuboot_config/mcuboot_config.h
@@ -60,7 +60,11 @@
 #if MYNEWT_VAL(BOOTUTIL_ENCRYPT_KW)
 #define MCUBOOT_ENCRYPT_KW 1
 #endif
-#if MYNEWT_VAL(BOOTUTIL_ENCRYPT_RSA) || MYNEWT_VAL(BOOTUTIL_ENCRYPT_KW)
+#if MYNEWT_VAL(BOOTUTIL_ENCRYPT_EC256)
+#define MCUBOOT_ENCRYPT_EC256 1
+#endif
+#if MYNEWT_VAL(BOOTUTIL_ENCRYPT_RSA) || MYNEWT_VAL(BOOTUTIL_ENCRYPT_KW) || \
+    MYNEWT_VAL(BOOTUTIL_ENCRYPT_EC256)
 #define MCUBOOT_ENC_IMAGES 1
 #endif
 #if MYNEWT_VAL(BOOTUTIL_OVERWRITE_ONLY)
diff --git a/boot/mynewt/mcuboot_config/syscfg.yml b/boot/mynewt/mcuboot_config/syscfg.yml
index ab3a47f..86821d1 100644
--- a/boot/mynewt/mcuboot_config/syscfg.yml
+++ b/boot/mynewt/mcuboot_config/syscfg.yml
@@ -46,6 +46,9 @@
     BOOTUTIL_ENCRYPT_KW:
         description: 'Support for encrypted images using AES-128-Keywrap.'
         value: 0
+    BOOTUTIL_ENCRYPT_EC256:
+        description: 'Support for encrypted images using ECIES-P256.'
+        value: 0
     BOOTUTIL_USE_MBED_TLS:
         description: 'Use mbed TLS for crypto operations.'
         value: 1