Fix #1065: don't validate Vulkan binding numbers.

To handle sparse assignments, don't check maxCombinedTextureImageUnits.

Test/vulkan.vert

@@ -58,3 +58,6 @@ out ban1 {                              // ERROR, only outer dimension
 out ban2 {
     float f;
 } bai2[arraySize][2];
+
+layout(binding = 3000) uniform sampler2D s3000;
+layout(binding = 3001) uniform b3001 { int a; };