ppc/pnv: Add QME region for P10

ppc/pnv: Add QME region for P10

The Quad Management Engine (QME) manages power related settings for its
quad. The xscom region is separate from the quad xscoms, therefore a new
region is added. The xscoms in a QME select a given core by selecting
the forth nibble.

Implement dummy reads for the stop state history (SSH) and special
wakeup (SPWU) registers. This quietens some sxcom errors when skiboot
boots on p10.

Power9 does not have a QME.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Message-ID: <20230707071213.9924-1-joel@jms.id.au>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>