Fix these warning:

acme@parisc:~/git/linux-2.6-tip$ make -C tools/perf/ install
make: Entering directory
`/home/acme/git/linux-2.6-tip/tools/perf' Makefile:833: warning:
overriding commands for target `perf-archive' Makefile:822:
warning: ignoring old commands for target `perf-archive'
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arnaldo 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: <1263846102-24841-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>