all: Format code to add space after C++-style comment start.

Note: the uncrustify configuration is explicitly set to 'add' instead of
'force' in order not to alter the comments which use extra spaces after //
as a means of indenting text for clarity.

lib/utils/printf.c

@@ -130,4 +130,4 @@ int snprintf(char *str, size_t size, const char *fmt, ...) {
     return ret;
 }
 
-#endif //MICROPY_USE_INTERNAL_PRINTF
+#endif // MICROPY_USE_INTERNAL_PRINTF

lib/utils/pyexec.c

@@ -168,7 +168,7 @@ typedef struct _repl_t {
     // but it was moved to MP_STATE_VM(repl_line) as containing
     // root pointer. Still keep structure in case more state
     // will be added later.
-    //vstr_t line;
+    // vstr_t line;
     bool cont_line;
     bool paste_mode;
 } repl_t;