ASoC: sun4i-i2s: Increase DMA max burst to 8

As done previously for sun4i-codec, the DMA maxburst of 4
is not supported by every SoCs so the DMA controller engine
returns "unsupported value".

As a maxburst of 8 is supported by all variants, this patch
increases it to 8.

For more details, see commit from Chen-Yu Tsai:
commit 730e2dd0 ("ASoC: sun4i-codec: Increase DMA max burst to 8")

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>