usb/xhci: refactor xhci_pci_setup()

xhci_pci_setup() is split into three pieces:

- xhci_gen_setup()
  The major remaining of xhci_pci_setup() is now containing the generic
  part of the xhci setup. It allocates the xhci struct, setup
  hcs_params? and friends, performs xhci_halt(), xhci_init and so one.
  It also obtains the quirks via a callback
- xhci_pci_quirks()
  It checks the origin of the xhci core and sets core specific quirks.
- xhci_pci_setup()
  PCI specific setup functions. Besides calling xhci_gen_setup() with
  xhci_pci_quirks() as an argument it performs PCI specific setup like
  obtaining the address of sbrn via a PCI config space.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>