The am53c974/dc390 PCI interrupt has two separate sources: the first is from the
internal ESP device, and the second is from the PCI DMA transfer logic.

Update the ESP interrupt handler so that it sets DMA_STAT_SCSIINT rather than
driving the PCI IRQ directly, and introduce a new esp_pci_update_irq() function
to generate the correct PCI IRQ level. In particular this fixes spurious interrupts
being generated by setting DMA_STAT_DONE at the end of a transfer if DMA_CMD_INTE_D
isn't set in the DMA_CMD register.

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: <20240112131529.515642-3-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
(cherry picked from commit 6b41417d934b2640b7ccf893544d656eea92a2e7)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>