Add ifdefs in crypto abstract function for ec256 to enable compilation when mbedtls used as backend

Signed-off-by: Roman Okhrimenko <roman.okhrimenko@cypress.com>
diff --git a/boot/bootutil/src/image_ec256.c b/boot/bootutil/src/image_ec256.c
index ef99381..185624c 100644
--- a/boot/bootutil/src/image_ec256.c
+++ b/boot/bootutil/src/image_ec256.c
@@ -29,6 +29,8 @@
 #include "mcuboot_config/mcuboot_config.h"
 
 #ifdef MCUBOOT_SIGN_EC256
+/*TODO: remove this after cypress port mbedtls to abstract crypto api */
+#if defined (MCUBOOT_USE_TINYCRYPT) || defined (MCUBOOT_USE_CC310)
 #include "bootutil/sign_key.h"
 
 #include "mbedtls/oid.h"
@@ -182,4 +184,5 @@
     return rc;
 }
 
+#endif /* MCUBOOT_USE_TINYCRYPT || defined MCUBOOT_USE_CC310 */
 #endif /* MCUBOOT_SIGN_EC256 */