tools/perf/arch/powerpc: Fix the CPU ID const char* value by adding 0x prefix

tools/perf/arch/powerpc: Fix the CPU ID const char* value by adding 0x prefix

Simple expression parser test fails in powerpc as below:

    4: Simple expression parser
    test child forked, pid 170385
    Using CPUID 004e2102
    division by zero
    syntax error
    syntax error
    FAILED tests/expr.c:65 parse test failed
    test child finished with -1
    Simple expression parser: FAILED!

This is observed after commit:
'commit 9d5da30e4ae9 ("perf jevents: Add a new expression builtin strcmp_cpuid_str()")'

With this commit, a new expression builtin strcmp_cpuid_str
got added. This function takes an 'ID' type value, which is
a string. So expression parse for strcmp_cpuid_str expects
const char * as cpuid value type. In case of powerpc, CPU IDs
are numbers. Hence it doesn't get interpreted correctly by
bison parser. Example in case of power9, cpuid string returns
as: 004e2102

cpuid of string type is expected in two cases:
1. char *get_cpuid_str(struct perf_pmu *pmu __maybe_unused);

   Testcase "tests/expr.c" uses "perf_pmu__getcpuid" which calls
   get_cpuid_str to get the cpuid string.

2. cpuid field in  :struct pmu_events_map

   struct pmu_events_map {
           const char *arch;
	   const char *cpuid;

   Here cpuid field is used in "perf_pmu__find_events_table"
   function as "strcmp_cpuid_str(map->cpuid, cpuid)". The
   value for cpuid field is picked from mapfile.csv.

Fix the mapfile.csv and get_cpuid_str function to prefix
cpuid with 0x so that it gets correctly interpreted by
the bison parser

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Tested-by: Disha Goel<disgoel@linux.ibm.com>
Cc: kjain@linux.ibm.com
Cc: maddy@linux.ibm.com
Cc: disgoel@linux.vnet.ibm.com
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20231009050052.64935-1-atrajeev@linux.vnet.ibm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>