Change error description

1. Change error description to a clearer one.
2. Change value in the error codes ranges description.
diff --git a/include/mbedtls/platform.h b/include/mbedtls/platform.h
index e30edc2..5cd143c 100644
--- a/include/mbedtls/platform.h
+++ b/include/mbedtls/platform.h
@@ -43,7 +43,7 @@
 #include "platform_time.h"
 #endif
 
-#define MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED       -0x0070 /**< Hardware failed platform operation. */
+#define MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED       -0x0070 /**< Hardware accelerator failed */
 
 #ifdef __cplusplus
 extern "C" {