staging: vme_user: remove open/release

Checking for image[minor].resource != NULL is not needed since all
resources are allocated before device is created.

image[minor].users accounting is deleted because it's not being used.

Signed-off-by: Dmitry Kalinkin <dmitry.kalinkin@gmail.com>
Cc: Igor Alekseev <igor.alekseev@itep.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>