pnv/xive2: Add NVG and NVC to cache watch facility

pnv/xive2: Add NVG and NVC to cache watch facility

The cache watch facility uses the same register interface to handle
entries in the NVP, NVG and NVC tables. A bit-field in the 'watchX
specification' register tells the table type. So far, that bit-field
was not read and the code assumed a read/write to the NVP table.

This patch allows to read/write entries in the NVG and NVC table as
well.

Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Kowal <kowal@linux.vnet.ibm.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>