perf report: Output non-zero offset for decompressed records

Print offset of PERF_RECORD_COMPRESSED record instead of zero for
decompressed records in raw trace dump (-D option of perf-report):

  0x17cf08 [0x28]: event: 9

instead of:

  0 [0x28]: event: 9

The fix is not critical, because currently file_pos for compressed
events is used in perf_session__process_event only to show offsets
in the raw dump.

This patch was separated from patchset:

https://lore.kernel.org/lkml/cover.1629186429.git.alexey.v.bayduraev@linux.intel.com/

and was already rewieved.
Reviewed-by: Riccardo Mancini <rickyman7@gmail.com>
Signed-off-by: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Tested-by: Riccardo Mancini <rickyman7@gmail.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Antonov <alexander.antonov@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210929091445.18274-1-alexey.v.bayduraev@linux.intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/session.c

@@ -2116,7 +2116,7 @@ fetch_decomp_event(u64 head, size_t mmap_size, char *buf, bool needs_swap)
 static int __perf_session__process_decomp_events(struct perf_session *session)
 {
 	s64 skip;
-	u64 size, file_pos = 0;
+	u64 size;
 	struct decomp *decomp = session->decomp_last;
 
 	if (!decomp)
@@ -2132,7 +2132,7 @@ static int __perf_session__process_decomp_events(struct perf_session *session)
 		size = event->header.size;
 
 		if (size < sizeof(struct perf_event_header) ||
-		    (skip = perf_session__process_event(session, event, file_pos)) < 0) {
+		    (skip = perf_session__process_event(session, event, decomp->file_pos)) < 0) {
 			pr_err("%#" PRIx64 " [%#x]: failed to process type: %d\n",
 				decomp->file_pos + decomp->head, event->header.size, event->header.type);
 			return -EINVAL;