perf lock contention: Fix memory sanitizer issue

perf lock contention: Fix memory sanitizer issue

The msan reported a use-of-uninitialized-value warning for the struct
lock_contention_data in lock_contention_read().  While it'd be filled
by bpf_map_lookup_elem(), let's just initialize it to silence the
warning.

  ==12524==WARNING: MemorySanitizer: use-of-uninitialized-value
  #0 0x562b0f16b1cd in lock_contention_read  util/bpf_lock_contention.c:139:7
  #1 0x562b0ef65ec6 in __cmd_contention  builtin-lock.c:1737:3
  #2 0x562b0ef65ec6 in cmd_lock  builtin-lock.c:1992:8
  #3 0x562b0ee7f50b in run_builtin  perf.c:322:11
  #4 0x562b0ee7efc1 in handle_internal_command  perf.c:376:8
  #5 0x562b0ee7e1e9 in run_argv  perf.c:420:2
  #6 0x562b0ee7e1e9 in main  perf.c:550:3
  #7 0x7f065f10e632 in __libc_start_main (/usr/lib64/libc.so.6+0x61632)
  #8 0x562b0edf2fa9 in _start (perf+0xfa9)
  SUMMARY: MemorySanitizer: use-of-uninitialized-value (perf+0xe15160) in lock_contention_read

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221028180128.3311491-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>