compositor-drm: Look through all crtc/encoder combinations

We used to only check the first possible encoder, now we go through all
possible encoders and look through all possible crtcs for each encoder.
diff --git a/weston.ini b/weston.ini
index 3c98e48..f736c8a 100644
--- a/weston.ini
+++ b/weston.ini
@@ -12,6 +12,7 @@
 #lockscreen=/usr/share/backgrounds/gnome/Garden.jpg
 #homescreen=/usr/share/backgrounds/gnome/Blinds.jpg
 #animation=fade
+
 [launcher]
 icon=/usr/share/icons/gnome/24x24/apps/utilities-terminal.png
 path=/usr/bin/gnome-terminal
@@ -32,3 +33,10 @@
 # Uncomment path to disable screensaver
 path=/usr/libexec/weston-screensaver
 duration=600
+
+[output]
+name=LVDS1
+mode=off
+
+mode=1366x768
+modeline=36.25 912 936 1024 1136  512 515 525 533 -hsync +vsync