tls: fix guards for ECDSA support

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/ssl_client.c b/library/ssl_client.c
index eab84c1..c0d0214 100644
--- a/library/ssl_client.c
+++ b/library/ssl_client.c
@@ -375,7 +375,7 @@
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2) && \
         (defined(MBEDTLS_KEY_EXCHANGE_SOME_ECDH_OR_ECDHE_1_2_ENABLED) || \
-        defined(MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED) || \
+        defined(MBEDTLS_KEY_EXCHANGE_ECDSA_CERT_REQ_ALLOWED_ENABLED) || \
         defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED))
         *tls12_uses_ec |= mbedtls_ssl_ciphersuite_uses_ec(ciphersuite_info);
 #endif