Staging: winbond: wb35reg: avoided use of extern function

Prototype of a function added to the header to avoid the use of extern.

Signed-off-by: Iker Pedrosa <ikerpedrosam@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>