perf test: Fix typo

Its 'multiple', not 'mutliple', noticed while preparing a talk for
Linuxtag'13.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-dzy9nl1ku7a5umddvdic4ibl@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/builtin-test.c

@@ -70,7 +70,7 @@ static struct test {
 		.func = test__attr,
 	},
 	{
-		.desc = "Test matching and linking mutliple hists",
+		.desc = "Test matching and linking multiple hists",
 		.func = test__hists_link,
 	},
 	{