kconfig: document oldnoconfig to what it really does in conf.c

As 67d34a6a39 said, the make target
'oldnoconfig' is a misnomer. It doesn't set new symbols to 'n', but
instead sets it to their default values.

This patch fixes the document in conf.c, and will submit another patch
to replace 'oldnoconfig' to 'olddefconfig'

Signed-off-by: Adam Lee <adam8157@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/kconfig/conf.c

@@ -467,7 +467,7 @@ static void conf_usage(const char *progname)
 	printf("  --oldaskconfig          Start a new configuration using a line-oriented program\n");
 	printf("  --oldconfig             Update a configuration using a provided .config as base\n");
 	printf("  --silentoldconfig       Same as oldconfig, but quietly, additionally update deps\n");
-	printf("  --oldnoconfig           Same as silentoldconfig but set new symbols to no\n");
+	printf("  --oldnoconfig           Same as silentoldconfig but sets new symbols to their default value\n");
 	printf("  --defconfig <file>      New config with default defined in <file>\n");
 	printf("  --savedefconfig <file>  Save the minimal current configuration to <file>\n");
 	printf("  --allnoconfig           New config where all options are answered with no\n");