In case of error, the function devm_ioremap_resource() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check should
be replaced with IS_ERR().
Signed-off-by: NWei Yongjun <weiyj.lk@gmail.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>