fixup: Make the fields of mbedtls_ecp_curve_info public

Remove more places where MBEDTLS_PRIVATE() was used on grp_id, which is now
public.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/programs/pkey/ecdsa.c b/programs/pkey/ecdsa.c
index 6b6e951..550a230 100644
--- a/programs/pkey/ecdsa.c
+++ b/programs/pkey/ecdsa.c
@@ -51,7 +51,7 @@
 #define ECPARAMS    MBEDTLS_ECP_DP_SECP192R1
 
 #if !defined(ECPARAMS)
-#define ECPARAMS    mbedtls_ecp_curve_list()->MBEDTLS_PRIVATE(grp_id)
+#define ECPARAMS    mbedtls_ecp_curve_list()->grp_id
 #endif
 
 #if !defined(MBEDTLS_ECDSA_C) || !defined(MBEDTLS_SHA256_C) || \