Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Merge with latest version of the Mylex 6+ driver.

- All sources are built in a single object, reducing namespace pollution.
- Kill the ready queue, and handle a busy response to mly_start in callers
rather than deferring the command.
- Improve our interaction with CAM:
- Don't advertise physical channels as SCSI busses by default.
- use the SIM queue freeze capability rather than queueing CDBs internally.
- force bus reprobe at module load time.
- Clean up more resources in mly_free.
- Tidy up debugging levels.
- Tidy up handling of events (mostly just code cleanliness).
- Use explanatory macros for operations on bus/target/channel numbers.

Use a consistent style and one much closer to the rest of /usr/src

This is the initial import of a new driver for the current family of
PCI:SCSI RAID controllers from Mylex.