clk: qcom: krait-cc: fix wrong pointer passed to IS_ERR()

It should be 'mux' passed to IS_ERR/PTR_ERR().

Fixes: 56a655e1 ("clk: qcom: krait-cc: convert to parent_data API")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230104080235.1748953-1-yangyingliang@huawei.com