In case of error, the function devm_platform_get_and_ioremap_resource()
returns ERR_PTR() and never returns NULL. The NULL test in the return
value check should be replaced with IS_ERR().

Fixes: 453ed428 ("reset: mchp: sparx5: add switch reset driver")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20210519141638.3052456-1-weiyongjun1@huawei.comSigned-off-by: NPhilipp Zabel <p.zabel@pengutronix.de>