ASoC: cs35l56: Fix an unsigned comparison which can never be negative

The variable 'rv' is defined as unsigned type, so the following if
statement is invalid, we can modify the type of rv to int.
if (rv < 0) {
dev_err(cs35l56->dev, "irq: failed to get pm_runtime:
%d\n", rv);
goto err_unlock;
}

./sound/soc/codecs/cs35l56.c:333:5-7: WARNING: Unsigned expression compared with zero: rv < 0.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=4599
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230324022303.121485-1-jiapeng.chong@linux.alibaba.com
Signed-off-by: Mark Brown <broonie@kernel.org>