drm: fix a bad VERSION check.

I found why my G5 was crashing when using the linux-2.6 version of the
DRM + git-drm.patch from 2.6.13-rc6-mm1, but not with the CVS DRM.
The reason was that dev->agp->cant_use_aperture wasn't getting set,
and the reason for that was that <linux/version.h> no longer gets
included and the #if LINUX_VERSION_CODE < 0x020408 in drm_agpsupport.c
was going the wrong way.  With this patch (and a few others) a 32-bit
server works correctly, as does DRI.

From: Paul Mackerras <paulus@samba.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>