Deprecate hardware acceleration errors
Deprecate the module-specific XXX_HW_ACCEL_FAILED and
XXX_FEATURE_UNAVAILABLE errors, as alternative implementations should now
return `MBEDTLS_ERR_PLATFORM_HW_FAILED` and
`MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED`.
diff --git a/include/mbedtls/sha256.h b/include/mbedtls/sha256.h
index 33aff28..47a31e8 100644
--- a/include/mbedtls/sha256.h
+++ b/include/mbedtls/sha256.h
@@ -36,6 +36,7 @@
#include <stddef.h>
#include <stdint.h>
+/* MBEDTLS_ERR_SHA256_HW_ACCEL_FAILED is deprecated and should not be used. */
#define MBEDTLS_ERR_SHA256_HW_ACCEL_FAILED -0x0037 /**< SHA-256 hardware accelerator failed */
#ifdef __cplusplus