vc4: Fix the shader record size for extended strides.

It turns out they aren't packed when attributes are missing, according to
both docs and simulation.

v2: Drop unused variable.

src/gallium/drivers/vc4/vc4_simulator_validate.c

@@ -94,7 +94,10 @@ gl_shader_rec_size(uint32_t pointer_bits)
 	if (attribute_count == 0)
 		attribute_count = 8;
 
-	return 36 + attribute_count * (extended ? 12 : 8);
+	if (extended)
+		return 100 + attribute_count * 4;
+	else
+		return 36 + attribute_count * 8;
 }
 
 static bool