perf symbols: Set dso->kernel when handling the fake vmlinux MMAP event

Because it may be possible that there was no buildid section,
where we would set this to 1.

Found while analysing a perf.data file collected on an ARM
machine where an explicitely specified vmlinux was being
disregarded.
Reported-by: NJamie Iles <jamie.iles@picochip.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1263904574-30732-1-git-send-email-acme@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

tools/perf/util/event.c

@@ -373,6 +373,7 @@ int event__process_mmap(event_t *self, struct perf_session *session)
 			if (kernel == NULL)
 				goto out_problem;
 
+			kernel->kernel = 1;
 			if (__map_groups__create_kernel_maps(&session->kmaps,
 							     session->vmlinux_maps,
 							     kernel) < 0)