Use common is_ctrl_char() helper function

This modifies couple of code segments that replaced control characters
in strings with '_' to use a common helper function.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/utils/common.h

@@ -554,6 +554,7 @@ size_t utf8_escape(const char *inp, size_t in_size,
 		   char *outp, size_t out_size);
 size_t utf8_unescape(const char *inp, size_t in_size,
 		     char *outp, size_t out_size);
+int is_ctrl_char(char c);
 
 
 /*