staging: vme: correct array overflow

Eric Sesterhenn noticed that vme_user is overflowing an array used by
sprintf. Use a bigger array.

CC: Eric Sesterhenn <eric.sesterhenn@lsexperts.de>
Signed-off-by: Martyn Welch <martyn.welch@gefanuc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>