i915 warning on skylake with current master (12f03ee)

I didn't see before (see the dmesg output below). The display manager (sddm) also refuse to start at first complaining X "stopped" but could start if I restart it from the terminal. I also attached the output of `lspci -v` in case it is useful. Yichao Yu --

Memory order of `mprotect`

uarantee stated here though it's unclear to me if future optimization of the kernel code could break this guarentee. Thanks. Yichao Yu