drm: Handle dev->unique with drmm_

We need to add a drmm_kstrdup for this, but let's start somewhere.

This is not exactly perfect onion unwinding, but it's jsut a kfree so
doesn't really matter at all.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-21-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_managed.c

@@ -167,6 +167,22 @@ void *drmm_kmalloc(struct drm_device *dev, size_t size, gfp_t gfp)
 }
 EXPORT_SYMBOL(drmm_kmalloc);
 
+char *drmm_kstrdup(struct drm_device *dev, const char *s, gfp_t gfp)
+{
+	size_t size;
+	char *buf;
+
+	if (!s)
+		return NULL;
+
+	size = strlen(s) + 1;
+	buf = drmm_kmalloc(dev, size, gfp);
+	if (buf)
+		memcpy(buf, s, size);
+	return buf;
+}
+EXPORT_SYMBOL_GPL(drmm_kstrdup);
+
 void drmm_kfree(struct drm_device *dev, void *data)
 {
 	struct drmres *dr_match = NULL, *dr;