vexpress: Re-enable building of perf for standard vexpress builds

Perf now builds OK, so re-enable it.

This reverts commit 89089670 (vexpress: Disable building of perf for
standard vexpress builds)

Change-Id: I7f6592dda57a357804be10f0e7e23adb9ee0f84e
Signed-off-by: Jon Medhurst <tixy@linaro.org>
1 file changed