staging: refer to TODO in Kconfig help text

Refer to TODO file instead of driver_name.README that does not seem to be
used.
Signed-off-by: NAaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/Kconfig

@@ -16,8 +16,8 @@ menuconfig STAGING
 
 	  If you wish to work on these drivers, to help improve them, or
 	  to report problems you have with them, please see the
-	  driver_name.README file in the drivers/staging/ directory to
-	  see what needs to be worked on, and who to contact.
+	  drivers/staging/<driver_name>/TODO file to see what needs to be
+	  worked on, and who to contact.
 
 	  If in doubt, say N here.