library: add remaining changes for the new ECP_LIGHT symbol

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/psa/crypto_extra.h b/include/psa/crypto_extra.h
index 7ff90eb..e8cecf7 100644
--- a/include/psa/crypto_extra.h
+++ b/include/psa/crypto_extra.h
@@ -573,7 +573,7 @@
  * @{
  */
 
-#if defined(MBEDTLS_ECP_C)
+#if defined(MBEDTLS_ECP_LIGHT)
 #include <mbedtls/ecp.h>
 
 /** Convert an ECC curve identifier from the Mbed TLS encoding to PSA.
@@ -660,7 +660,7 @@
 mbedtls_ecp_group_id mbedtls_ecc_group_of_psa(psa_ecc_family_t curve,
                                               size_t bits,
                                               int bits_is_sloppy);
-#endif /* MBEDTLS_ECP_C */
+#endif /* MBEDTLS_ECP_LIGHT */
 
 /**@}*/