libdrm README rename

[Michel Dänzer]

On 2019-01-29 2:16 a.m., Dave Airlie wrote:
> So libdrm README renamed to README.rst, however that means it no
> longer gets included in the dist tarball.
> 
> I think autotools considers README special, so we might need to fix it,

Adding the new README file to EXTRA_DIST seems enough, see e.g.
https://gitlab.freedesktop.org/xorg/driver/xf86-video-amdgpu/commit/a9da219e13bd0cdec65554382b5cd15abc3e3778
.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer