perf tools: Initialize dso->node member in dso__new

perf tools: Initialize dso->node member in dso__new

If dso->node member is not initialized, it causes a segmentation fault when
adding to other lists.

It should be initilized in dso__new().

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
LKML-Reference: : <20100421195616.24664.89980.stgit@localhost6.localdomain6>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>