interconnect: imx: Fix return value check in imx_icc_node_init_qos()

interconnect: imx: Fix return value check in imx_icc_node_init_qos()

In case of error, the function of_parse_phandle() returns NULL pointer
not ERR_PTR(). The IS_ERR() test in the return value check should be
replaced with NULL test.

Fixes: f0d8048525d7 ("interconnect: Add imx core driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Link: https://lore.kernel.org/r/20200509030214.14435-1-weiyongjun1@huawei.com
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>