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 r261004, r261005 and r261033:
Adjust the DMA delay logic so that the DMA delay does not become too small.

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

Approved by: re (implicit)

This patch adds automatic detection of USB mass storage devices
which does not support the no synchronize cache SCSI command.

The __FreeBSD_version version macro has been bumped and
external kernel modules needs to be recompiled after
this patch.

Approved by: re (kib)
MFC after: 1 week
PR: usb/160299

Improve enumeration of Low- and Full-speed devices connected through a
High-speed USB HUB by resetting the transaction translator (TT)
before trying re-enumeration. Also when clear-stall fails multiple times
try a re-enumeration.

Suggested by: Trevor Blackwell
MFC after: 14 days

Add more sanity checks for USB_HOST_ALIGN input values. Re-factor existing
checks for readability.

Approved by: thompsa (mentor)

Allow USB_HOST_ALIGN to be configured at compile time. This patch is
necessary for MIPS based RouterStation Pro board and maybe other MIPS
based boards as well.

Submitted by: Milan Obuch
Approved by: thompsa (mentor)

Make USB packet filtering code optional.

Approved by: thompsa (mentor)

Add possibility to generate devctl notifications regardless of UGEN presence.

Submitted by: Nick Hibma
Approved by: thompsa (mentor)

Change USB_DEBUG to #ifdef and allow it to be turned off. Previously this had
the illusion of a tunable setting but was always turned on regardless.

MFC after: 1 week

- Make struct usb_xfer opaque so that drivers can not access the internals
- Reduce the number of headers needed for a usb driver, the common case is just usb.h and usbdi.h