[media] media: stk1160: Add Kconfig help on snd-usb-audio requirement

The Kconfig currently makes no reference to the snd-usb-audio
driver, which supports audio capture for this type of devices.
Just in case, let's make sure the requirement is mentioned
in the description.
Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/stk1160/Kconfig

@@ -6,7 +6,11 @@ config VIDEO_STK1160_COMMON
 	  This is a video4linux driver for STK1160 based video capture devices.
 
 	  To compile this driver as a module, choose M here: the
-	  module will be called stk1160
+	  module will be called stk1160.
+
+	  This driver only provides support for video capture. For audio
+	  capture, you need to select the snd-usb-audio driver (i.e.
+	  CONFIG_SND_USB_AUDIO).
 
 config VIDEO_STK1160
 	tristate