Staging: w35und: make wb35_probe() and wb35_disconnect() funtions static

The wb35_probe() and wb35_disconnect() functions are only used in wbusb.c so
make them static and remove them from a header file.

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