-ENOTSUPP is not a SUSV4 error code and should not be used. Use
-ENOPROTOOPT instead to report EC_RES_INVALID_VERSION responses
from the EC. This matches match the NFS response for unsupported
protocol versions.

Cc: Gwendal Grignou <gwendal@chromium.org>
Cc: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Cc: Prashant Malani <pmalani@chromium.org>
Cc: Brian Norris <briannorris@chromium.org>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>