esp: move handle_ti_cmd() cleanup code to esp_do_dma().

esp: move handle_ti_cmd() cleanup code to esp_do_dma().

To prepare following patches move do_cmd and DMA special case
from handle_ti() to esp_do_dma().

This part of the code must be only executed with real DMA, not with
pseudo-DMA. And PDMA is detected in esp_do_dma(), so move this part
of the code in esp_do_dma(). We keep the code in handle_ti_cmd()
in the case no DMA is done.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20191026164546.30020-2-laurent@vivier.eu>