staging: pi433: use help in Kconfig description

Fixes checkpatch warning:

  WARNING: prefer 'help' over '---help---' for new help texts
Signed-off-by: Valentin Vidic <Valentin.Vidic@CARNet.hr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/pi433/Kconfig

 config PI433
         tristate "Pi433 - a 433MHz radio module for Raspberry Pi"
         depends on SPI
-        ---help---
+        help
           This option allows you to enable support for the radio module Pi433.
 
           Pi433 is a shield that fits onto the GPIO header of a Raspberry Pi