powerpc/pseries: Move PLPKS constants to header file

[ Upstream commit 3def7a3e ]

Move the constants defined in plpks.c to plpks.h, and standardise their
naming, so that PLPKS consumers can make use of them later on.

Signed-off-by: Russell Currey <ruscur@russell.cc>
Co-developed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230210080401.345462-16-ajd@linux.ibm.com


Stable-dep-of: 78435434 ("powerpc/pseries: make max polling consistent for longer H_CALLs")
Signed-off-by: Sasha Levin <sashal@kernel.org>