powerpc/mm: Only define MAX_PHYSMEM_BITS in SPARSEMEM configurations

[Andreas Schwab]

On Mär 25 2019, Michael Ellerman <mpe at ellerman.id.au> wrote:

> So I'm inclined to just switch to always using SPARSEMEM on 64-bit
> Book3S, because that's what's well tested and we hardly need more code
> paths to test. Unless anyone has a strong objection, I haven't actually
> benchmarked FLATMEM vs SPARSEMEM on a G5.

Configuring with SPARSEMEM saves about 32Mb of memory.

Andreas.

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Andreas Schwab, schwab at linux-m68k.org
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