Rename the sha384 checksum context to reflect its purpose

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index 64e134d..2b9ac5c 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -1410,7 +1410,7 @@
         psa_hash_abort( &ssl->handshake->fin_sha384_psa );
         psa_hash_setup( &ssl->handshake->fin_sha384_psa, PSA_ALG_SHA_384 );
 #else
-        mbedtls_sha512_starts( &ssl->handshake->fin_sha512, 1 );
+        mbedtls_sha512_starts( &ssl->handshake->fin_sha384, 1 );
 #endif
 #endif /* MBEDTLS_SHA384_C */
     }