Doc: usb: chipidea: need to build both kernel Image and modules

When tried to enable OTG FSM, we need to rebuild both kernel Image
and modules, since there are some codes at gadget modules which are
controlled by related configurations.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/usb/chipidea.txt b/Documentation/usb/chipidea.txt
index 4c0e2ea..995c8bc 100644
--- a/Documentation/usb/chipidea.txt
+++ b/Documentation/usb/chipidea.txt
@@ -5,7 +5,7 @@
 
 1.1 How to enable OTG FSM in menuconfig
 ---------------------------------------
-Select CONFIG_USB_OTG_FSM.
+Select CONFIG_USB_OTG_FSM, rebuild kernel Image and modules.
 If you want to check some internal variables for otg fsm,
 select CONFIG_USB_CHIPIDEA_DEBUG, there are 2 files which
 can show otg fsm variables and some controller registers value: