render/vulkan: fix undefined reference to wlr_texture_is_vk

Added the  implement of wlr_texture_is_vk.

Fixes: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3419

render/vulkan/texture.c

@@ -7,14 +7,19 @@
 #include <sys/stat.h>
 #include <unistd.h>
 #include <wlr/render/wlr_texture.h>
+#include <wlr/render/vulkan.h>
 #include <wlr/util/log.h>
 #include "render/pixel_format.h"
 #include "render/vulkan.h"
 
 static const struct wlr_texture_impl texture_impl;
 
+bool wlr_texture_is_vk(struct wlr_texture *wlr_texture) {
+	return wlr_texture->impl == &texture_impl;
+}
+
 struct wlr_vk_texture *vulkan_get_texture(struct wlr_texture *wlr_texture) {
-	assert(wlr_texture->impl == &texture_impl);
+	assert(wlr_texture_is_vk(wlr_texture));
 	return (struct wlr_vk_texture *)wlr_texture;
 }