PCI/ERR: Avoid negated conditional for clarity

PCI/ERR: Avoid negated conditional for clarity

Reverse the sense of the Root Port/Downstream Port conditional for clarity.
No functional change intended.

Link: https://lore.kernel.org/r/20201121001036.8560-9-sean.v.kelley@intel.com
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> # non-native/no RCEC
Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>