tools: perf: add perf-periodic

Add the 'periodic' command to perf. This allows collection
of counters at a specified interval.

Change-Id: I4e42ac3f21cbdf2c196dbd01d31e6dc6051efd7e
Signed-off-by: Neil Leeder <nleeder@codeaurora.org>
(cherry picked from commit 4832fc26190f5cd4270cd6813bca120c51e75744)