device/*/linux-*: enable CONFIG_DEVPTS_MULTIPLE_INSTANCES for <4.7
This is required for kernels earlier than 4.7 for bwrap to work for normal users, and therefore for gnome web (epiphany) and flatpak.
This is required for kernels earlier than 4.7 for bwrap to work for normal users, and therefore for gnome web (epiphany) and flatpak.