drm/i915: Move pinning to inside engine_wa_list_verify()

This should be done as part of the ww loop, in order to remove a
i915_vma_pin that needs ww held.

Now only i915_ggtt_pin() callers remaining.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210323155059.628690-25-maarten.lankhorst@linux.intel.com