gvt-fixes-2020-02-12

- fix possible high-order allocation fail for late load (Igor)
- fix one missed lock for ppgtt mm LRU list (Igor)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
From: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200212065912.GB4997@zhen-hp.sh.intel.com