buffers: support per-numa-domain buffer size

buffers: support per-numa-domain buffer size

Currently, buffers-per-numa is used for all NUMA domains, and there's
no way to allocate different amounts for each domain.

Therefore, this adds a per-NUMA-domain buffer config section, which
currently has a single option to set the number of buffers.

If it's not specified or set to zero, the code falls back to
buffers-per-numa as before.

Type: improvement
Change-Id: If35d7a9eff6f8d1d78063ea7873dbf50780d0ec3
Signed-off-by: Lukas Stockner <[email protected]>