Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r265015:
Setting the IMOD value below 0x3F8 can cause IRQ lockups in the Intel
LynxPoint USB 3.0 controllers found in MacBookPro 2013's.

MFC r264340:
Correct IMOD default value according to comment.

MFC r251249, r251251, r251252, r?\0242512, r251254 and r251515:
Correct XHCI DMA descriptor programming.
Correct maximum IRQ rate.

MFC r238551 and r239617:
Add support for Intel Panther/Lynx Point XHCI port routing.

MFC r227396, r227401, r227541, r227654 and r228493:
Relax XHCI timeouts which should fix enumeration issues.
Fix definition of XHCI port power bit.
Correct size of some USB 3.0 descriptor fields.

Reported by: Kohji Okuno, Jan Henrik Sylvester

MFC r226803:
Fix suspend and resume of non-super-speed USB devices
in the generic XHCI driver. There appears to be some minor
logic missing for this feature to work.

Approved by: re (kib)

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Renamed PCI_INTERFACE_XHCI to PCIP_SERIALBUS_USB_XHCI and moved it
to <dev/pci/pcireg.h>.

Reviewed by: hselasky
MFC after: 3 days

Commit initial version of new XHCI driver which was written from
scratch. This driver adds support for USB3.0 devices. The XHCI
interface is also backwards compatible to USB2.0 and USB1.0 and will
evntually replace the OHCI/UHCI and EHCI drivers.

There will be follow-up commits during the coming week to link the
driver into the default kernel build and add missing USB3.0
functionality in the USB core. Currently only the driver files are
committed.

Approved by: thompsa (mentor)