Fix bogus usage message in pio tool.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>

pio.c

@@ -168,7 +168,10 @@ static const char *argv0;
 static void usage(int rc )
 {
 
-	fprintf(stderr, "usage: %s [-m|-i input] [-o output] pin..\n", argv0);
+	fprintf(stderr, "usage: %s -m|-i input [-o output] pin..\n", argv0);
+	fprintf(stderr," -m				mmap - read pin state from system\n");
+	fprintf(stderr," -i				read pin state from file\n");
+	fprintf(stderr," -o				save pin state data to file\n");
 	fprintf(stderr," print				Show all pins\n");
 	fprintf(stderr," Pxx				Show pin\n");
 	fprintf(stderr," Pxx<mode><pull><drive><data>	Configure pin\n");