perf off_cpu: Fix a typo in BTF tracepoint name, it should be 'btf_trace_sched_switch'

perf off_cpu: Fix a typo in BTF tracepoint name, it should be 'btf_trace_sched_switch'

In BTF, tracepoint definitions have the "btf_trace_" prefix.  The
off-cpu profiler needs to check the signature of the sched_switch event
using that definition.  But there's a typo (s/bpf/btf/) so it failed
always.

Fixes: b36888f71c8542cd ("perf record: Handle argument change in sched_switch")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: bpf@vger.kernel.org
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20221208182636.524139-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>