ppc: introducing spapr_numa.c NUMA code helper

ppc: introducing spapr_numa.c NUMA code helper

We're going to make changes in how spapr handles all
ibm,associativity* related properties to enhance our current NUMA
support.

At this moment we have associativity code scattered all around
spapr_* files, with hardcoded values and array sizes. This
makes it harder to change any NUMA specific parameters in
the future. Having everything in the same place allows not
only for easier tuning, but also easier understanding since all
NUMA related code is on the same file.

This patch introduces a new file to gather all NUMA/associativity
handling code in spapr, spapr_numa.c. To get things started, let's
remove associativity-reference-points and max-associativity-domains
code from spapr_dt_rtas() to a new helper called spapr_numa_write_rtas_dt().
This will decouple spapr_dt_rtas() from the NUMA changes that
are going to happen in those two properties.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20200901125645.118026-2-danielhb413@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>