Restore SHA256 & SHA512 prototypes

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/tf-psa-crypto/drivers/builtin/src/sha512.c b/tf-psa-crypto/drivers/builtin/src/sha512.c
index 25ac70b..52b4f62 100644
--- a/tf-psa-crypto/drivers/builtin/src/sha512.c
+++ b/tf-psa-crypto/drivers/builtin/src/sha512.c
@@ -737,7 +737,7 @@
     }
 }
 
-static int mbedtls_internal_sha512_process(mbedtls_sha512_context *ctx,
+int mbedtls_internal_sha512_process(mbedtls_sha512_context *ctx,
                                     const unsigned char data[SHA512_BLOCK_SIZE])
 {
     if (mbedtls_a64_crypto_sha512_has_support()) {