configure.ac: raise Mako required version to 0.8.0

configure.ac: raise Mako required version to 0.8.0

It seems [0] old versions of Mako are no longer supported. Emil mentioned it
might need v0.8.0 [1] for isl_format_layout [2], although I didn't get
a confirmation that it's really the minimum.
Let's raise it to that to avoid getting other bugs.
We might lower it a bit again later if it turns out we can.

[0] https://lists.freedesktop.org/archives/mesa-dev/2016-July/122772.html
[1] https://lists.freedesktop.org/archives/mesa-dev/2016-July/122775.html
[2] https://lists.freedesktop.org/archives/mesa-dev/2016-July/123278.html

Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Acked-by: Dave Airlie <Airlied@redhat.com>