Replace for loop with while in shader

Author: nicopap

crates/bevy_pbr/src/render/parallax_mapping.wgsl

@@ -41,8 +41,8 @@ fn parallaxed_uv(
     var current_layer_height = 0.0;
     var current_height = sample_depth_map(uv);
 
-    let int_max_layer_count = i32(max_layer_count);
-    for (var i: i32 = 0; i <= int_max_layer_count; i++)  {
+    // This at most runs layer_count times
+    while true {
         if (current_height <= current_layer_height) {
             break;
         }