Depth 30 enablement for ati-ddx + exa.

[Mario Kleiner]

Hi,

this is the patch series for ati-ddx to enable depth 30
color display under exa, which i used for testing the
corresponding mesa 30 bit rendering patches. Works well,
and photometer measurements confirmed we get 10 bpc per
color channel.

1/3 fixes a server crash if x-screen depth 30 is selected.

2/3 is actually Fredrik Hoeglunds work, which he sent out many
years ago to the mailing list. I've tested it without problems
on HD 5770 for the evergreen exa path, and on some HD 4000 series
(rv630 iirc) for the r600 exa path, and it seems to work nicely.

It also has a r-b by me as in "looks good to me", but i'm
not familiar enough with exa to really judge if it is complete or
if something for some more unusual case might be missing.

I guess it also might need a signed off by Fredrik?

3/3 switches depth 30 on for exa + Linux 3.16 and later, when depth
30 scanout was added to radeon-kms.

Thanks,
-mario