dri3: Add missing libdrm dependency in Makefile.am

Fixes: 0ce93e5b "dri3: Include dix-config.h instead of
                     xorg-config.h"
Signed-off-by: Dor Askayo <dor.askayo@gmail.com>
4 jobs for dri3-missing-dependency in 6 minutes and 8 seconds (queued for 1 second)