Staging: w35und: move source files to one directory

As we're trying to get rid of the "compatability layer" in the driver, move
everything under one directory. Keeping some of the files under
drivers/staging/winbond/linux is a major pain in the ass whenever you're
cleaning up the driver.

Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>