ata: acard-ahci: Remove call to memset after dmam_alloc_coherent

In commit af7ddd8a
("Merge tag 'dma-mapping-4.21' of git://git.infradead.org/users/hch/dma-mapping"),
dmam_alloc_coherent has already zeroed the memory.
So memset is not needed.
Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/ata/acard-ahci.c

@@ -344,7 +344,6 @@ static int acard_ahci_port_start(struct ata_port *ap)
 	mem = dmam_alloc_coherent(dev, dma_sz, &mem_dma, GFP_KERNEL);
 	if (!mem)
 		return -ENOMEM;
-	memset(mem, 0, dma_sz);
 
 	/*
 	 * First item in chunk of DMA memory: 32-slot command table,