perf was in the oldpackages repository, but it makes more sense to have
it part of the default package set since we build it from the Linux
kernel sources.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43418 3c298f89-4303-0410-b956-a3cf2f4a3e73