tools/perf/powerpc/util: Add support to handle compatible mode PVR for perf json events

perf list picks the events supported for specific platform
from pmu-events/arch/powerpc/<platform>. Example power10 events
are in pmu-events/arch/powerpc/power10, power9 events are part
of pmu-events/arch/powerpc/power9. The decision of which
platform to pick is determined based on PVR value in powerpc.
The PVR value is matched from pmu-events/arch/powerpc/mapfile.csv

Example:

Format:
	PVR,Version,JSON/file/pathname,Type

0x004[bcd][[:xdigit:]]{4},1,power8,core
0x0066[[:xdigit:]]{4},1,power8,core
0x004e[[:xdigit:]]{4},1,power9,core
0x0080[[:xdigit:]]{4},1,power10,core
0x0082[[:xdigit:]]{4},1,power10,core

The code gets the PVR from system using get_cpuid_str function
in arch/powerpc/util/headers.c ( from SPRN_PVR ) and compares
with value from mapfile.csv
In case of compat mode, say when partition is booted in a power9
mode when the system is a power10, this picks incorrectly. Because
PVR will point to power10 where as it should pick events from power9
folder. To support generic events, add new folder
pmu-events/arch/powerpc/compat to contain the ISA architected events
which is supported in compat mode. Also return 0x00ffffff as pvr
when booted in compat mode. Based on this pvr value, json will
pick events from pmu-events/arch/powerpc/compat

Suggested-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Tested-by: Disha <Goel&lt;disgoel@linux.ibm.com>
Cc: akanksha@linux.ibm.com
Cc: hbathini@linux.ibm.com
Cc: kjain@linux.ibm.com
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20241010145107.51211-2-atrajeev@linux.vnet.ibm.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>