perf tools: Fix eBPF event specification parsing

perf tools: Fix eBPF event specification parsing

Looks like I've reached the new level of stupidity, adding missing braces.

Committer testing:

Given the following eBPF C filter, that will add a record when it
returns true, i.e. when the tv_nsec variable is > 2000ns, should be
built and installed via sys_bpf(), but fails to do so before this patch:

  # cat filter.c
  #include <uapi/linux/bpf.h>
  #define SEC(NAME) __attribute__((section(NAME), used))

  SEC("func=hrtimer_nanosleep rqtp->tv_nsec")
  int func(void *ctx, int err, long nsec)
  {
	  return nsec > 1000;
  }
  char _license[] SEC("license") = "GPL";
  int _version SEC("version") = LINUX_VERSION_CODE;
  #

  # perf trace -e nanosleep,filter.c usleep 1
  invalid or unsupported event: 'filter.c'
  Run 'perf list' for a list of valid events

   Usage: perf trace [<options>] [<command>]
      or: perf trace [<options>] -- <command> [<options>]
      or: perf trace record [<options>] [<command>]
      or: perf trace record [<options>] -- <command> [<options>]

      -e, --event <event>   event/syscall selector. use 'perf list' to list available events
  #

And works again after it is applied, the nothing is inserted when the co

  # perf trace -e *sleep,filter.c usleep 1
     0.000 ( 0.066 ms): usleep/23994 nanosleep(rqtp: 0x7ffead94a0d0) = 0
  # perf trace -e *sleep,filter.c usleep 2
     0.000 ( 0.008 ms): usleep/24378 nanosleep(rqtp: 0x7fffa021ba50) ...
     0.008 (         ): perf_bpf_probe:func:(ffffffffb410cb30) tv_nsec=2000)
     0.000 ( 0.066 ms): usleep/24378  ... [continued]: nanosleep()) = 0
  #

The intent of 9445464bb831 is kept:

  # perf stat -e 'cpu/uops_executed.core,krava/'  true
  event syntax error: '..cuted.core,krava/'
                                    \___ unknown term

  valid terms: cmask,pc,event,edge,in_tx,any,ldlat,inv,umask,in_tx_cp,offcore_rsp,config,config1,config2,name,period
  Run 'perf list' for a list of valid events

   Usage: perf stat [<options>] [<command>]

      -e, --event <event>   event selector. use 'perf list' to list available events
  #
  # perf stat -e 'cpu/uops_executed.core,period=1/'  true

   Performance counter stats for 'true':

           808,332      cpu/uops_executed.core,period=1/

       0.002997237 seconds time elapsed

  #

Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Fixes: 9445464bb831 ("perf tools: Unwind properly location after REJECT")
Link: http://lkml.kernel.org/n/tip-diea0ihbwpxfw6938huv3whj@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>