perf_counter tools: Initialize a stack variable before use

the "perf report" utility crashed in some circumstances
because the "sym" stack variable was not initialized before used
(as also proven by valgrind).

With this fix both the crash goes away and valgrind no longer complains.
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

tools/perf/util/symbol.c

@@ -457,6 +457,8 @@ static int dso__load_sym(struct dso *self, int fd, const char *name,
 
 	nr_syms = shdr.sh_size / shdr.sh_entsize;
 
+	memset(&sym, 0, sizeof(sym));
+
 	elf_symtab__for_each_symbol(syms, nr_syms, index, sym) {
 		struct symbol *f;
 		uint64_t obj_start;