atp870u: Use pci_request_regions

Use pci_request_regions and do it before accessing the I/O ports.
Also add missing pci_disable_device() call to atp870u_remove().

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>