perf script: Fix hangup in offline flamegraph report

perf script: Fix hangup in offline flamegraph report

A recent change in the flamegraph script fixed an issue with live mode
but it created another for offline mode.  It needs to pass "-" to -i
option to read from stdin in the live mode.  Actually there's a logic
to pass the option in the perf script code, but the script was written
with "-- $@" which prevented the option to go to the perf script.  So
the previous commit added the hard-coded "-i -" to the report command.

But it's a problem for the offline mode which expects input from a file
and now it's stuck on reading from stdin.  Let's remove the "-i - --"
part and let it pass the options properly to perf script.

Closes: https://lore.kernel.org/linux-perf-users/c41e4b04-e1fd-45ab-80b0-ec2ac6e94310@linux.ibm.com
Fixes: 23e0a63c6dd3f69c ("perf script: force stdin for flamegraph in live mode")
Reported-by: Thomas Richter <tmricht@linux.ibm.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Anubhav Shelat <ashelat@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>