package/mesa3d-headers: also install dri header and .pc file

Building GL with Xorg requires the DRI interface.

Provide that header and pkg-config file for those binary blobs
that do not provide them.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Jérôme Pouiller <jezz@sysmic.org>
Cc: Bernd Kuhls <berndkuhls@hotmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>