powerpc/mpc86xx_hpcn: Remove obsolete statement

Comment says "Delete this in 2.6.27".

Do so now.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a47bb6a69c68156bc2d555152dab5a23733856b7.1630667612.git.christophe.leroy@csgroup.eu