Change restart context type.

No need to have both x509 and ecdsa, as the former contains the later.
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index db57713..7ffeb5b 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -2615,7 +2615,7 @@
 
 #if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
         if( ssl->handshake->ecrs_enabled )
-            rs_ctx = &ssl->handshake->ecrs_ctx;
+            rs_ctx = &ssl->handshake->ecrs_ctx.ecdsa;
 #endif
 
         if( ( ret = mbedtls_pk_verify_restartable(
@@ -3290,7 +3290,7 @@
 
 #if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
     if( ssl->handshake->ecrs_enabled )
-        rs_ctx = &ssl->handshake->ecrs_ctx;
+        rs_ctx = &ssl->handshake->ecrs_ctx.ecdsa;
 #endif
 
     if( ( ret = mbedtls_pk_sign_restartable( mbedtls_ssl_own_key( ssl ),