PCI: Rename pci_flr_wait() to pci_dev_wait() and make it generic

PCIe r4.0, sec 2.3.1, Request Handling Rules, says:

  Valid reset conditions after which a device is permitted to return CRS
  are:
  * Cold, Warm, and Hot Resets,
  * FLR
  * A reset initiated in response to a D3hot to D0 uninitialized

Try to reuse FLR implementation towards other reset types.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>