staging: VME: Remove PIO2 driver

The PIO2 device is (as far as I know) no longer manufactured. I no longer
have access to the device and this seems unlikely to change. The only
changes to this driver in a long time have been as a result of API changes
else where. Time to remove it...

Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>