Rename the sha384 checksum context to reflect its purpose

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index e76086a..f019ad2 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -794,7 +794,7 @@
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
     psa_hash_operation_t fin_sha384_psa;
 #else
-    mbedtls_sha512_context fin_sha512;
+    mbedtls_sha512_context fin_sha384;
 #endif
 #endif