perf scripts python: Fix passing arguments to stackcollapse report

The '--' prevented arguments from being passed to the script, such as:

  $ perf script report stackcollapse -i my_perf.data
Signed-off-by: Michael Petlan <mpetlan@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
LPU-Reference: 20200427142327.21172-1-mpetlan@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/scripts/python/bin/stackcollapse-report

 #!/bin/sh
 # description: produce callgraphs in short form for scripting use
-perf script -s "$PERF_EXEC_PATH"/scripts/python/stackcollapse.py -- "$@"
+perf script -s "$PERF_EXEC_PATH"/scripts/python/stackcollapse.py "$@"