streamlining the sym2 io submission path

[Matthew Wilcox <matthew@wil.cx>]

I've been looking at speeding up sym2's queuecommand method.  In my
current development tree, I've removed most of sym_queue_command()
and inlined the remains into sym53c8xx_queuecommand().  There's some
funny stuff I wouldn't mind some advice with:

We fail the first command to the device if the device is marked as
NOSCAN or the lun is non-0 and the device isn't marked as SCAN LUNS.
I think the first part should be moved to slave_alloc(); it's a little
weird, but supportable.  The second part troubles me a little -- is the
blacklist in the midlayer good enough to handle this, or should I leave
this mechanism in?

The driver currently fails commands sent to the lun of the host adapter.
Is this the correct behaviour?  What should the driver do?

-- 
"Next the statesmen will invent cheap lies, putting the blame upon 
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince 
himself that the war is just, and will thank God for the better sleep 
he enjoys after this process of grotesque self-deception." -- Mark Twain