mm/mm_init.c: move build check on MAX_ZONELISTS out of ifdef

Current check on MAX_ZONELISTS is wrapped in CONFIG_DEBUG_MEMORY_INIT,
which may not be triggered all the time.

Let's move it out to a more general place.

Link: https://lkml.kernel.org/r/20240619010612.20740-2-richard.weiyang@gmail.com


Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>