xircom_cb: fix device probe error path.

- unbalanced pci_disable_device
- PCI ressources were not released
- mismatching pci_alloc_.../kfree pairs are replaced by DMA alloc helpers.

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Ack-by: Grant Grundler <grundler@parisc-linux.org>