drm/framebuffer: Fix use of uninitialized variable

smatch reports:

drivers/gpu/drm/drm_framebuffer.c:654 drm_mode_getfb2_ioctl() error: uninitialized symbol 'ret'.

'ret' is possibly not set when there are no errors, causing the error
above. I can't say if that ever happens in real-life, but in any case I
think it is good to initialize 'ret' to 0.
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231103-uninit-fixes-v2-2-c22b2444f5f5@ideasonboard.com

drivers/gpu/drm/drm_framebuffer.c

@@ -583,7 +583,7 @@ int drm_mode_getfb2_ioctl(struct drm_device *dev,
 	struct drm_mode_fb_cmd2 *r = data;
 	struct drm_framebuffer *fb;
 	unsigned int i;
-	int ret;
+	int ret = 0;
 
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
 		return -EINVAL;