Don't iterate the whole /sys/devices just to find drm device

On some large systems, /sys/devices is huge and it's not a wise idea to
iterate it. `find` may cause tremendous contention on the kernfs_mutex
when there are already stress on /sys, and it will perform very very
poorly.

Simply check if drm class presents should be good enough.

Signed-off-by: Kairui Song <kasong@redhat.com>
Acked-by: Pingfan Liu <piliu@redhat.com>

dracut-module-setup.sh

@@ -58,7 +58,7 @@ depends() {
         _dep="$_dep znet"
     fi
 
-    if [ -n "$( find /sys/devices -name drm )" ] || [ -d /sys/module/hyperv_fb ]; then
+    if [ -n "$( ls -A /sys/class/drm 2>/dev/null )" ] || [ -d /sys/module/hyperv_fb ]; then
         add_opt_module drm
     fi