perf trace: Fix call-graph output

Recently, Arnaldo fixed global vs event specific --max-stack usage with
commit bd3dda9ab0fb ("perf trace: Allow overriding global --max-stack
per event"). This commit is having a regression when we don't use
--max-stack at all with perf trace. Ex,

$ ./perf trace record -g ls
$ ./perf trace -i perf.data
0.076 ( 0.002 ms): ls/9109 brk(
0.196 ( 0.008 ms): ls/9109 access(filename: 0x9f998b70, mode: R
0.209 ( 0.031 ms): ls/9109 open(filename: 0x9f998978, flags: CLOEXEC

This is missing call-traces.
After patch:

$ ./perf trace -i perf.data
0.076 ( 0.002 ms): ls/9109 brk(
do_syscall_trace_leave ([kernel.kallsyms])
[0] ([unknown])
syscall_exit_work ([kernel.kallsyms])
brk (/usr/lib64/ld-2.17.so)
_dl_sysdep_start (/usr/lib64/ld-2.17.so)
_dl_start_final (/usr/lib64/ld-2.17.so)
_dl_start (/usr/lib64/ld-2.17.so)
_start (/usr/lib64/ld-2.17.so)
0.196 ( 0.008 ms): ls/9109 access(filename: 0x9f998b70, mode: R
do_syscall_trace_leave ([kernel.kallsyms])
[0] ([unknown])

Signed-off-by: Ravi Bangoria <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Fixes: bd3dda9ab0fb ("perf trace: Allow overriding global --max-stack per event")
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-trace.c

···
 				    struct callchain_cursor *cursor)
 {
 	struct addr_location al;
+	int max_stack = evsel->attr.sample_max_stack ?
+			evsel->attr.sample_max_stack :
+			trace->max_stack;
 
 	if (machine__resolve(trace->host, &al, sample) < 0 ||
-	    thread__resolve_callchain(al.thread, cursor, evsel, sample, NULL, NULL, evsel->attr.sample_max_stack))
+	    thread__resolve_callchain(al.thread, cursor, evsel, sample, NULL, NULL, max_stack))
 		return -1;
 
 	return 0;