core: mbedtls: sm2: fix SM2 key generation

ecc_get_keysize() lacks a case for TEE_ECC_CURVE_SM2, which prevents the
generation of a SM2 key pair. Fix this.

Signed-off-by: Jerome Forissier <jerome@forissier.org>
Reviewed-by: Etienne Carriere <etienne.carriere@linaro.org>
diff --git a/lib/libmbedtls/core/ecc.c b/lib/libmbedtls/core/ecc.c
index 4acc601..0fc0d77 100644
--- a/lib/libmbedtls/core/ecc.c
+++ b/lib/libmbedtls/core/ecc.c
@@ -91,6 +91,13 @@
 		    (algo != TEE_ALG_ECDH_P521))
 			return TEE_ERROR_BAD_PARAMETERS;
 		break;
+	case TEE_ECC_CURVE_SM2:
+		*key_size_bits = 256;
+		*key_size_bytes = 32;
+		if (algo != 0 && algo != TEE_ALG_SM2_DSA_SM3 &&
+		    algo != TEE_ALG_SM2_KEP && algo != TEE_ALG_SM2_PKE)
+			return TEE_ERROR_BAD_PARAMETERS;
+		break;
 	default:
 		*key_size_bits = 0;
 		*key_size_bytes = 0;