radeon, DVI and coherent_mode

[Simon Thum]

Hi,

I've just rebuilt my system's ati driver, and now it's missing the
'coherent_mode' RandR prop.

This might be correct, as I only abused this prop to reinit stuff until
my display stopped showing blackouts (happens from time to time, so this
saves me restarting xorg).

In case this is accidental, I've got:
01:00.1 Display controller: ATI Technologies Inc RV280 [Radeon 9200]
(Secondary) (rev 01)
DVI connected DFP
No KMS or GEM