[POWERPC] 86xx: mark functions static, other minor cleanups

Cleanups as suggested by Stephen Rothwell and Dale Farnsworth, which
incudes marking a bunch of functions static and add a vendor prefix to
the compat node check for uniqueness.

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