Input: wacom - make sure touch_max is set for touch devices

Old single touch Tablet PCs do not have touch_max set at
wacom_features. Since touch device at lease supports one
finger, assign touch_max to 1 when touch usage is defined
in its HID Descriptor and touch_max is not pre-defined.

Tested-by: Jason Gerecke <[e-mail]>
Signed-off-by: Ping Cheng <[e-mail]>
Reviewed-by: Chris Bagwell <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/tablet/wacom_sys.c

···
 	struct usb_device *dev = interface_to_usbdev(intf);
 	char limit = 0;
 	/* result has to be defined as int for some devices */
-	int result = 0;
+	int result = 0, touch_max = 0;
 	int i = 0, usage = WCM_UNDEFINED, finger = 0, pen = 0;
 	unsigned char *report;
 
···
 				if (usage == WCM_DESKTOP) {
 					if (finger) {
 						features->device_type = BTN_TOOL_FINGER;
-
+						/* touch device at least supports one touch point */
+						touch_max = 1;
 						switch (features->type) {
 						case TABLETPC2FG:
 							features->pktlen = WACOM_PKGLEN_TPC2FG;
···
 	}
 
  out:
+	if (!features->touch_max && touch_max)
+		features->touch_max = touch_max;
 	result = 0;
 	kfree(report);
 	return result;