DISCONTIGMEM is deprecated

[Matthew Wilcox]

On Fri, Apr 19, 2019 at 10:43:35AM +0100, Mel Gorman wrote:
> DISCONTIG is essentially deprecated and even parisc plans to move to
> SPARSEMEM so there is no need to be fancy, this patch simply disables
> watermark boosting by default on DISCONTIGMEM.

I don't think parisc is the only arch which uses DISCONTIGMEM for !NUMA
scenarios.  Grepping the arch/ directories shows:

alpha (does support NUMA, but also non-NUMA DISCONTIGMEM)
arc (for supporting more than 1GB of memory)
ia64 (looks complicated ...)
m68k (for multiple chunks of memory)
mips (does support NUMA but also non-NUMA)
parisc (both NUMA and non-NUMA)

I'm not sure that these architecture maintainers even know that DISCONTIGMEM
is deprecated.  Adding linux-arch to the cc.