perf symbols: Check the right return variable

In function dso__split_kallsyms(), curr_map saves the return value
of map__new2. So check it instead of var map after the call returns.

Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: <stable@kernel.org> # for .33.x
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>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1267066851.1726.9.camel@localhost>
Signed-off-by: Ingo Molnar <mingo@elte.hu>