Minor style changes

1. Rephrase error description.
2. fix alignment of error list.
diff --git a/library/error.c b/library/error.c
index d3b155b..c629217 100644
--- a/library/error.c
+++ b/library/error.c
@@ -827,7 +827,7 @@
 
 #if defined(MBEDTLS_PLATFORM_C)
     if( use_ret == -(MBEDTLS_ERR_PLATFORM_HW_FAILED) )
-        mbedtls_snprintf( buf, buflen, "PLATFORM - Hardware platform function failed" );
+        mbedtls_snprintf( buf, buflen, "PLATFORM - Hardware failed platform operation" );
 #endif /* MBEDTLS_PLATFORM_C */
 
 #if defined(MBEDTLS_POLY1305_C)