xdriver_xf86-video-ati: fix dependencies

This package depends on the radeon driver from libdrm and depends on
DRI support in xserver_xorg-server, to achieve this we select the
Radeon mesa3d DRI driver.

Fixes:
http://autobuild.buildroot.net/results/9da/9da4ffdf1c4ec78ae37322e253cb769340116035



Signed-off-by: Lada Trimasova <ltrimas@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>