ata: sata_sil24: 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/sata_sil24.c

@@ -1202,7 +1202,6 @@ static int sil24_port_start(struct ata_port *ap)
 	cb = dmam_alloc_coherent(dev, cb_size, &cb_dma, GFP_KERNEL);
 	if (!cb)
 		return -ENOMEM;
-	memset(cb, 0, cb_size);
 
 	pp->cmd_block = cb;
 	pp->cmd_block_dma = cb_dma;