start removing block bounce buffering support v3

Hi all,

this series starts to clean up and remove the impact of the legacy old
block layer bounce buffering code.

First it removes support for ISA bouncing.  This was used by three SCSI
drivers.  One of them actually had an active user and developer 5 years
ago so I've converted it to use a local bounce buffer - Ondrej, can you
test the coversion?  The next one has been known broken for years, and
the third one looks like it has no users for the ISA support so they
are just dropped.

It then removes support for dealing with bounce buffering highmem pages
for passthrough requests as we can just use the copy instead of the map
path for them.  This will reduce efficiency for such setups on highmem
systems (e.g. usb-storage attached DVD drives), but then again that is
what you get for using a driver not using modern interfaces on a 32-bit
highmem system.  It does allow to streamline the common path pretty nicely.


Changes since v2:
 - remove more dead code in advansys.c
 - remove more dead code in BusLogic.c
 - update the BusLogic documentation

Changes since v1:
 - remove more dead code in advansys.c
 - fix the bounce limit stacking in blk_stack_limits