vme: tsi148: fix DMA lists longer that one item

DMA lists on tsi148 weren't processed further than the first item
because of the broken logic. This regression was introduced in:

ac1a4f2c "Staging: VME: Ensure TSI148 link list descriptors..."

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>