dma_alloc_coherent() already clears the allocated memory, there is no need
to explicitly call memset().

Moreover, it is likely that the size in the memset() is incorrect and
should be "size * sizeof(*ring->desc)".
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/d5acce7dd108887832c9719f62c7201b4c83b3fb.1676184599.git.christophe.jaillet@wanadoo.frSigned-off-by: Jakub Kicinski <kuba@kernel.org>