drm/i915/gt: Always force restore freshly pinned contexts

It is highly unlikely, but still conceivable, that we submit a context
with the same GGTT address as last active on the HW. In this case, with
a matching LRCA, the HW would not restore the new context image causing
a potential violation of our context isolation.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200107172842.3315449-1-chris@chris-wilson.co.uk