PCI: endpoint: pci-epf-test: register notifier if only core_init_notifier is enabled

Need to register pci_epf_test_notifier function even if only
core_init_notifier is enabled.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Acked-by: Om Prakash Singh <omp@nvidia.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>