gallium: add new cap PIPE_CAP_DEVICE_PROTECTED_CONTENT

Will be used to implement EGL_EXT_protected_surface.

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5096>
3 files changed