media: imx-jpeg: Remove unnecessary memset() after dma_alloc_coherent()

[ Upstream commit 2bcc3b48 ]

The `dma_alloc_coherent()' already zeroes out memory for us, so we don't
need the redundant memset().

Signed-off-by: Jason Wang <wangborong@cdjrlc.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Stable-dep-of: 46e9c092 ("media: imx-jpeg: Move mxc_jpeg_free_slot_data() ahead")
Signed-off-by: Sasha Levin <sashal@kernel.org>