staging: vme_user: mark user-space buffers with __user

Signed-off-by: Emilio G. Cota <cota@braap.org>
[martyn.welch@ge.com: modified to remove checkpatch warnings]
Signed-off-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>