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/include/bootutil/crypto/ecdsa_p256.h b/boot/bootutil/include/bootutil/crypto/ecdsa_p256.h
index a43b96e..faa8ea3 100644
--- a/boot/bootutil/include/bootutil/crypto/ecdsa_p256.h
+++ b/boot/bootutil/include/bootutil/crypto/ecdsa_p256.h
@@ -13,7 +13,8 @@
 #include "mcuboot_config/mcuboot_config.h"
 
 #if (defined(MCUBOOT_USE_TINYCRYPT) + \
-     defined(MCUBOOT_USE_CC310)) != 1
+     defined(MCUBOOT_USE_CC310) + \
+     defined(MCUBOOT_USE_MBED_TLS)) != 1
     #error "One crypto backend must be defined: either CC310 or TINYCRYPT"
 #endif
 
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 */