dmaengine: at_xdmac: Remove a level of indentation in at_xdmac_advance_work()

It's easier to read code with fewer levels of indentation, remove a level
of indentation in at_xdmac_advance_work()

if (!foo() & !bar()) {
}

was replaced by:

if (foo() || bar())
	return;

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20211215110115.191749-9-tudor.ambarus@microchip.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>