Call for testers, users with scsi cards

[Jeff Roberson]

http://people.freebsd.org/~jeff/loadccb.diff

This patch consolidates all of the functions that map cam control blocks 
for DMA into one central function.  This change is a precursor to adding 
new features to the I/O stack.  It is mostly mechanical.  If you are 
running current on a raid or scsi card, especially if it is a lesser used 
one, I would really like you to apply this patch and report back any 
problems.  If it works you should notice nothing.  If it doesn't work you 
will probably panic immediately on I/O or otherwise no I/O will happen.

Thanks,
Jeff