esp: defer command completion interrupt on incoming data transfers

esp: defer command completion interrupt on incoming data transfers

The MacOS toolbox ROM issues a command to the ESP controller as part of its
"FAST" SCSI routines and then proceeds to read the incoming data soon after
receiving the command completion interrupt.

Unfortunately due to SCSI block transfers being asynchronous the incoming data
may not yet be present causing an underflow error. Resolve this by waiting for
the SCSI subsystem transfer_data callback before raising the command completion
interrupt.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210304221103.6369-34-mark.cave-ayland@ilande.co.uk>