perf scripts python: export-to-postgresql.py: Fix struct.pack() int argument

Python 3.8 is requiring that arguments being packed as integers are also
integers.  Add int() accordingly.

 Before:

   $ perf record -e intel_pt//u uname
   $ perf script --itrace=bep -s ~/libexec/perf-core/scripts/python/export-to-postgresql.py perf_data_db branches calls
   2020-06-25 16:09:10.547256 Creating database...
   2020-06-25 16:09:10.733185 Writing to intermediate files...
   Traceback (most recent call last):
     File "/home/ahunter/libexec/perf-core/scripts/python/export-to-postgresql.py", line 1106, in synth_data
       cbr(id, raw_buf)
     File "/home/ahunter/libexec/perf-core/scripts/python/export-to-postgresql.py", line 1058, in cbr
       value = struct.pack("!hiqiiiiii", 4, 8, id, 4, cbr, 4, MHz, 4, percent)
   struct.error: required argument is not an integer
   Fatal Python error: problem in Python trace event handler
   Python runtime state: initialized

   Current thread 0x00007f35d3695780 (most recent call first):
   <no Python frame>
   Aborted (core dumped)

 After:

   $ dropdb perf_data_db
   $ rm -rf perf_data_db-perf-data
   $ perf script --itrace=bep -s ~/libexec/perf-core/scripts/python/export-to-postgresql.py perf_data_db branches calls
   2020-06-25 16:09:40.990267 Creating database...
   2020-06-25 16:09:41.207009 Writing to intermediate files...
   2020-06-25 16:09:41.270915 Copying to database...
   2020-06-25 16:09:41.382030 Removing intermediate files...
   2020-06-25 16:09:41.384630 Adding primary keys
   2020-06-25 16:09:41.541894 Adding foreign keys
   2020-06-25 16:09:41.677044 Dropping unused tables
   2020-06-25 16:09:41.703761 Done

Fixes: aba44287 ("perf scripts python: export-to-postgresql.py: Export Intel PT power and ptwrite events")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200629091955.17090-2-adrian.hunter@intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>