perf test amd ibs: Fix incorrect kernel version check

perf test amd ibs: Fix incorrect kernel version check

"AMD IBS sample period" unit test is getting skipped on kernel v7.x. Fix
the kernel version >= v6.15 check.

Fixes: 21fb366b2f457611 ("perf test amd: Skip amd-ibs-period test on kernel < v6.15")
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ananth Narayan <ananth.narayan@amd.com>
Cc: Dapeng Mi <dapeng1.mi@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Manali Shukla <manali.shukla@amd.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Santosh Shukla <santosh.shukla@amd.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>