blankpad(niri): 180-degree flip of both external panels

DP-2 270->90, HDMI-A-1 90->270. In portrait, 180 is the 90<->270 swap.

dotfiles/zz-blankpad/niri/.config/niri/cfg/display.kdl

@@ -7,17 +7,17 @@
 //
 // Both external PM1601 panels run portrait. niri's transform is
 // counter-clockwise: "90" = panel's top bezel faces left, "270" = top bezel
-// faces right. DP-2 turns the other way from HDMI-A-1.
+// faces right. In portrait a 180° flip is the 90<->270 swap.
 
 output "DP-2" {
     scale 1
-    transform "270"
+    transform "90"
     position x=1536 y=0
 }
 
 output "HDMI-A-1" {
     scale 1
-    transform "90"
+    transform "270"
     position x=2736 y=0
 }