hw/scsi/esp-pci: use correct address register for PCI DMA transfers

hw/scsi/esp-pci: use correct address register for PCI DMA transfers

The current code in esp_pci_dma_memory_rw() sets the DMA address to the value
of the DMA_SPA (Starting Physical Address) register which is incorrect: this
means that for each callback from the SCSI layer the DMA address is set back
to the starting address.

In the case where only a single SCSI callback occurs (currently for transfer
lengths < 128kB) this works fine, however for larger transfers the DMA address
wraps back to the initial starting address, corrupting the buffer holding the
data transferred to the guest.

Fix esp_pci_dma_memory_rw() to use the DMA_WAC (Working Address Counter) for
the DMA address which is correctly incremented across multiple SCSI layer
transfers.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Message-ID: <20240112131529.515642-2-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>