mpc8641hpcn/sbc8641d: Add missing board_lmb_reserves

We're missing the board_lmb_reserve definitions that allow
cpu_mp_lmb_reserve to be called; this means that Linux
is free to reallocate reserved pages.  Linux currently boots
because we're getting lucky - the page we've reserved is
high enough in memory that it isn't allocated by Linux
while we still need it to be in existence.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>