staging: winbond: remove driver

The driver hasn't been cleaned up and nobody is working to do so, so
remove it.

Signed-off-by: Kristina Martšenko <kristina.martsenko@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>