sbc85x0: tidy up Makefile to use new configuration script.

sbc85x0: tidy up Makefile to use new configuration script.

Commit 804d83a5 allows us to move all the configuration
variation tweaks out of the top level Makefile and down
into the boards config header.  This takes advantage of
that for the sbc8540/sbc8560 boards.

There were a couple of cheezy comments pointing at incorrect
files, or files that don't exist, so I've cleaned those up too.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>