perf sched: Replace BUG_ON on invalid CPU with graceful skip

perf sched: Replace BUG_ON on invalid CPU with graceful skip

latency_switch_event(), latency_runtime_event(), and map_switch_event()
use BUG_ON(cpu >= MAX_CPUS || cpu < 0) to validate the sample CPU.
When PERF_SAMPLE_CPU is absent from the sample type,
evsel__parse_sample() initializes sample->cpu to (u32)-1.  Casting
this to int yields -1, which triggers the BUG_ON and aborts perf sched.

The central CPU validation in perf_session__deliver_event() intentionally
preserves the (u32)-1 sentinel for downstream tools like perf script
and perf inject, so leaf callbacks must handle it themselves.

Replace the three BUG_ON calls with graceful skips using pr_warning(),
matching the existing pattern in process_sched_switch_event() and
process_sched_runtime_event() earlier in the same file.  Include the
file offset for cross-referencing with perf report -D.

Reported-by: sashiko-bot@kernel.org # Running on a local machine
Reviewed-by: Ian Rogers <irogers@google.com>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>