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 <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: [e-mail]
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Song Liu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/bpf_off_cpu.c

···
 	const struct btf_type *t1, *t2, *t3;
 	u32 type_id;
 
-	type_id = btf__find_by_name_kind(btf, "bpf_trace_sched_switch",
+	type_id = btf__find_by_name_kind(btf, "btf_trace_sched_switch",
 					 BTF_KIND_TYPEDEF);
 	if ((s32)type_id < 0)
 		return;