Fix T97827: material preview not displaying textures

Caused by rB281bcc1c1dd6 which did not properly made use
of `vec4` for UVs which are now loaded as attributes.

source/blender/gpu/shaders/material/gpu_shader_material_bump.glsl

@@ -5,6 +5,13 @@ void differentiate_texco(vec3 v, out vec3 df)
   df = v + dF_impl(v);
 }
 
+/* Overload for UVs which are loaded as generic attributes. */
+void differentiate_texco(vec4 v, out vec3 df)
+{
+  /* Implementation defined. */
+  df = v.xyz + dF_impl(v.xyz);
+}
+
 void node_bump(
     float strength, float dist, float height, vec3 N, vec2 dHd, float invert, out vec3 result)
 {

source/blender/gpu/shaders/material/gpu_shader_material_texture_coordinates.glsl

@@ -1,7 +1,7 @@
 
 void node_tex_coord(mat4 obmatinv,
                     vec3 attr_orco,
-                    vec3 attr_uv,
+                    vec4 attr_uv,
                     out vec3 generated,
                     out vec3 normal,
                     out vec3 uv,
@@ -12,7 +12,7 @@ void node_tex_coord(mat4 obmatinv,
 {
   generated = attr_orco;
   normal = normal_world_to_object(g_data.N);
-  uv = attr_uv;
+  uv = attr_uv.xyz;
   object = transform_point((obmatinv[3][3] == 0.0) ? ModelMatrixInverse : obmatinv, g_data.P);
   camera = coordinate_camera(g_data.P);
   window = coordinate_screen(g_data.P);