[ATA] [patch] crashes, deadlock, memory leaks, . plus LSI RAID write support

I had to fix some ATA bugs to increase its robustness.

See a problem report and a patch at
	http://www.freebsd.org/cgi/query-pr.cgi?pr=92786

The patch enables a support for disk failures and enables hot-swapping 
SATA disks without a frequent system crash.
It deals with a deadlock in an ata-raid design that causes systems
to hang often on reboot, after RAID rebuild or in other situations. The 
patch implements additional locking to access RAID labels.
The patch implements partial reference counters
for ATA requests to avoid memory leaks or twice-freed requests
and crashes.

The patch includes support for writing RAID labels on LSIv3. This is the 
builtin SATA RAID on the current Intel Server Board (SE7520JR2).

More details are given in the problem report linked above.

In particular, the patch proposes an easy scheme for ATA RAID label
construction that if accepted will enabe to add GEOM layer
based on ATA RAID native labels at a later time, and reuse
label reading and filling up functions. This is not possible at present.

The patch was stable in our test, and I'd be glad
to find out how well it works for you.

Best,
Garry