We don't care about the result of the read, so it may be garbage, we
only care that the mmio is flushed. As such, we can forgo using an
individual forcewake and lock around any posting-read for an engine.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190703155225.9501-4-chris@chris-wilson.co.uk