perf tools: Fix pager on minimal-install embedded systems

perf tools: Fix pager on minimal-install embedded systems

Some Distributions may lack "less" package being included by default,
e.g., Linaro nano rootfs. In those cases use the portable "pager"
command instead of "less".

Signed-off-by: Avik Sil <avik.sil@linaro.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1338287725-26382-1-git-send-email-avik.sil@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>