m68k/mm: Set all online nodes in N_NORMAL_MEMORY

For m68k, N_NORMAL_MEMORY represents all nodes that have present memory
since it does not support HIGHMEM.  This patch sets the bit at the time
node_present_pages has been set by free_area_init_node.
At the time the node is brought online, the node state would have to be
done unconditionally since information about present memory has not yet
been recorded.

If N_NORMAL_MEMORY is not accurate, slub may encounter errors since it
uses this nodemask to setup per-cache kmem_cache_node data structures.

This pach is an alternative to the one proposed by David Rientjes
<rientjes@google.com> attempting to set node state immediately when
bringing the node online.

Signed-off-by: Michael Schmitz <schmitz@debian.org>
Tested-by: Thorsten Glaser <tg@debian.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
CC: stable@kernel.org