dmaengine: sh: rz-dmac: Add device_synchronize callback

dmaengine: sh: rz-dmac: Add device_synchronize callback

Some on-chip peripheral modules(for eg:- rspi) on RZ/G2L SoC
use the same signal for both interrupt and DMA transfer requests.
The signal works as a DMA transfer request signal by setting
DMARS, and subsequent interrupt requests to the interrupt controller
are masked.

We can re-enable the interrupt by clearing the DMARS.

This patch adds device_synchronize callback for clearing
DMARS and thereby allowing DMA consumers to switch to
interrupt mode.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20220722084430.969333-1-biju.das.jz@bp.renesas.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>