[POWERPC] 86xx: mpc86xx_hpcn - Temporarily accept old dts node identifier.

As suggested by Timur Tabi, we match on the old compat node ID for one
version and warn accordingly.  If we don't do this, we plunge people who
try to use an old DTB into silent boot death with no clear indication of
what the problem is.

This patch should be removed at the beginning of the 2.6.27 dev cycle.
It is only meant to ease the transition in the short term.

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