perf symbols: No need to check if sym->name is NULL

As it is an array, so will always evaluate to 'true', as reported by
clang:

  builtin-sched.c:2070:19: error: address of array 'sym->name' will always evaluate to 'true' [-Werror,-Wpointer-bool-conversion]
                  if (sym && sym->name) {
                          ~~ ~~~~~^~~~
  1 warning generated.

So just ditch all those useless checks.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-ydpm927col06paixb775jjx5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel_fprintf.c

@@ -168,7 +168,6 @@ int sample__fprintf_callchain(struct perf_sample *sample, int left_alignment,
 
 			if (symbol_conf.bt_stop_list &&
 			    node->sym &&
-			    node->sym->name &&
 			    strlist__has_entry(symbol_conf.bt_stop_list,
 					       node->sym->name)) {
 				break;