kconfig: Do not print status messages in make -s mode

Add an -s option to the various frontends and pass it when make -s is
used. Also, use $(kecho) instead of @echo in the Makefile.

Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
index fef75fc..6c20431 100644
--- a/scripts/kconfig/conf.c
+++ b/scripts/kconfig/conf.c
@@ -471,7 +471,7 @@
 static void conf_usage(const char *progname)
 {
 
-	printf("Usage: %s [option] <kconfig-file>\n", progname);
+	printf("Usage: %s [-s] [option] <kconfig-file>\n", progname);
 	printf("[option] is _one_ of the following:\n");
 	printf("  --listnewconfig         List new options\n");
 	printf("  --oldaskconfig          Start a new configuration using a line-oriented program\n");
@@ -501,7 +501,11 @@
 
 	tty_stdio = isatty(0) && isatty(1) && isatty(2);
 
-	while ((opt = getopt_long(ac, av, "", long_opts, NULL)) != -1) {
+	while ((opt = getopt_long(ac, av, "s", long_opts, NULL)) != -1) {
+		if (opt == 's') {
+			conf_set_message_callback(NULL);
+			continue;
+		}
 		input_mode = (enum input_mode)opt;
 		switch (opt) {
 		case silentoldconfig: