misc: pci_endpoint_test: Fix pci_endpoint_test not releasing resources on remove

sscanf(misc_device->name, DRV_MODULE_NAME ".%d", &id) in
pci_endpoint_test_remove() returns 0, which results in returning early
without releasing the resources.  This is as a result of misc_device not
having a valid name. Fix it here.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>