perf lock: Fix non-atomic max/time and min_time updates in contention_data

The update_contention_data() had a FIXME noting that max_time and
min_time updates lacked atomicity. Two CPUs could simultaneously read a
stale value, pass the comparison check and race on the write-back, with
the smaller value potentially overwriting the larger one and silently
corrupting the statistics.

Fix this by replacing the bare conditional assignments with a
bpf_loop()-based CAS retry loop. Each field tracks its own convergence
independently via max_done/min_done flags in cas_ctx, so a successful
CAS on one field is never retried even if the other field needs more
attempts.

Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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