clk: mmp: pxa168: fix return value check in pxa168_clk_init()

Fix the retrn value check which testing the wrong variable
in pxa168_clk_init().

Fixes: ab08aefc ("clk: mmp: add pxa168 DT support for clock driver")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>