esp.c: move buffer and TC logic into separate to/from device paths in esp_do_dma()

esp.c: move buffer and TC logic into separate to/from device paths in esp_do_dma()

The ultimate aim is to for esp_do_dma() behaviour to be determined by the SCSI
bus phase, in which case it is necessary to have separate to/from device paths.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: Helge Deller <deller@gmx.de>
Tested-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20240112125420.514425-11-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>