drm/i915: unpin on error in intel_vgpu_shadow_mm_pin()

[ Upstream commit 3792fc50 ]

Call intel_vgpu_unpin_mm() on this error path.

Fixes: 41874148

 ("drm/i915/gvt: Adding ppgtt to GVT GEM context after shadow pdps settled.")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/Y3OQ5tgZIVxyQ/WV@kili
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>