boot: zephyr: add ECIES-P256 configuration

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/boot/zephyr/CMakeLists.txt b/boot/zephyr/CMakeLists.txt
index f5e02c7..ee0710d 100644
--- a/boot/zephyr/CMakeLists.txt
+++ b/boot/zephyr/CMakeLists.txt
@@ -113,7 +113,7 @@
   ${BOOT_DIR}/bootutil/src/tlv.c
   )
 
-if(CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256)
+if(CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256 OR CONFIG_BOOT_ENCRYPT_EC256)
   zephyr_library_include_directories(
 	${MBEDTLS_ASN1_DIR}/include
   )
@@ -165,6 +165,16 @@
   )
 endif()
 
+if(CONFIG_BOOT_ENCRYPT_EC256)
+  zephyr_library_sources(
+    ${TINYCRYPT_DIR}/source/aes_encrypt.c
+    ${TINYCRYPT_DIR}/source/aes_decrypt.c
+    ${TINYCRYPT_DIR}/source/ctr_mode.c
+    ${TINYCRYPT_DIR}/source/hmac.c
+    ${TINYCRYPT_DIR}/source/ecc_dh.c
+    )
+endif()
+
 if(CONFIG_MCUBOOT_SERIAL)
   zephyr_sources(${BOOT_DIR}/zephyr/serial_adapter.c)
   zephyr_sources(${BOOT_DIR}/boot_serial/src/boot_serial.c)