ASoC: sun4i-i2s: Replace call to params_channels by local variable

The sun4i_i2s_hw_params already has a variable holding the value returned
by params_channels, so let's just use that variable instead of calling
params_channels multiple times.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://lore.kernel.org/r/c0faaac69ad40248f24eed3c3b2fa1ccc4a85b70.1566242458.git-series.maxime.ripard@bootlin.com


Signed-off-by: Mark Brown <broonie@kernel.org>