Parse private key in uecc format

Parse the private key from cert in uecc format.
Accept only P-256 curve.
diff --git a/include/mbedtls/oid.h b/include/mbedtls/oid.h
index 48f0b30..0b8a7fa 100644
--- a/include/mbedtls/oid.h
+++ b/include/mbedtls/oid.h
@@ -471,6 +471,18 @@
 int mbedtls_oid_get_oid_by_pk_alg( mbedtls_pk_type_t pk_alg,
                            const char **oid, size_t *olen );
 
+#if defined(MBEDTLS_USE_TINYCRYPT)
+typedef enum
+{
+    MBEDTLS_UECC_DP_NONE = 0,       /*!< Curve not defined. */
+    MBEDTLS_UECC_DP_SECP256R1,      /*!< Domain parameters for the 256-bit curve defined by FIPS 186-4 and SEC1. */
+} mbedtls_uecc_group_id;
+
+int mbedtls_oid_get_ec_grp( const mbedtls_asn1_buf *oid, mbedtls_uecc_group_id *grp_id );
+
+int mbedtls_oid_get_oid_by_ec_grp( mbedtls_uecc_group_id grp_id, 
+                            const char **oid, size_t *olen);
+#else
 #if defined(MBEDTLS_ECP_C)
 /**
  * \brief          Translate NamedCurve OID into an EC group identifier
@@ -494,6 +506,7 @@
 int mbedtls_oid_get_oid_by_ec_grp( mbedtls_ecp_group_id grp_id,
                            const char **oid, size_t *olen );
 #endif /* MBEDTLS_ECP_C */
+#endif
 
 #if defined(MBEDTLS_MD_C)
 /**