perf symbols: Fix vmlinux path when not using --symfs

The ec5761ea cset introduced the symfs feature with a bug for loading vmlinux
files that ended up causing this failure:

[root@emilia v2.6.38-rc5+]# strace -e trace=open perf top --vmlinux ./vmlinux 2>&1 | tail -3
open("/./vmlinux", O_RDONLY)            = -1 ENOENT (No such file or directory)
./vmlinux with build id b9266bf40e98dadb5d43a2f3e95d3c5d4aff46dc not found, continuing without symbols
The ./vmlinux file can't be used
[root@emilia v2.6.38-rc5+]#

Remove the extra slash, just like is done in the DSO__ORIG_DSO handling in
dso__load() and other parts of the ec5761ea cset.
Reported-by: NIngo Molnar <mingo@elte.hu>
Cc: David Ahern <daahern@cisco.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol.c

@@ -1836,7 +1836,7 @@ int dso__load_vmlinux(struct dso *self, struct map *map,
 	int err = -1, fd;
 	char symfs_vmlinux[PATH_MAX];
 
-	snprintf(symfs_vmlinux, sizeof(symfs_vmlinux), "%s/%s",
+	snprintf(symfs_vmlinux, sizeof(symfs_vmlinux), "%s%s",
 		 symbol_conf.symfs, vmlinux);
 	fd = open(symfs_vmlinux, O_RDONLY);
 	if (fd < 0)