Minor style changes

1. Rephrase error description.
2. fix alignment of error list.
diff --git a/include/mbedtls/platform.h b/include/mbedtls/platform.h
index cb21d2a..5f5b982 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_FAILED       -0x0080 /**< Hardware platform function failed. */
+#define MBEDTLS_ERR_PLATFORM_HW_FAILED       -0x0080 /**< Hardware failed platform operation. */
 
 #ifdef __cplusplus
 extern "C" {