[PATCH] Lock scd(4): test or the driver will be removed

This patch adds locking to scd(4) and marks it MPSAFE.  It also uses bus_*() 
instead of bus_space_*().  The patch is against HEAD but probably applies to 9 
and 10 as well.

http://people.freebsd.org/~jhb/patches/scd_locking.patch

Note that this driver is using a deprecated API that will be removed in 11.  
If no one tests updates to this driver then it is not feasible to continue 
maintaining it in the tree.  In that case, it will be removed from HEAD one 
month from today.

-- 
John Baldwin