auxdisplay/ht16k33: Use struct fb_info.screen_buffer

Use info->screen_buffer when reading and writing framebuffers in
system memory. It's the correct pointer for this address space.

The struct fb_info has a union to store the framebuffer memory. This can
either be info->screen_base if the framebuffer is stored in I/O memory,
or info->screen_buffer if the framebuffer is stored in system memory.

As the driver operates on the latter address space, it is wrong to use
.screen_base and .screen_buffer must be used instead. This also gets
rid of casting needed due to not using the correct data type.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230428122452.4856-3-tzimmermann@suse.de

drivers/auxdisplay/ht16k33.c

@@ -640,7 +640,7 @@ static int ht16k33_fbdev_probe(struct device *dev, struct ht16k33_priv *priv,
 
 	INIT_DELAYED_WORK(&priv->work, ht16k33_fb_update);
 	fbdev->info->fbops = &ht16k33_fb_ops;
-	fbdev->info->screen_base = (char __iomem *) fbdev->buffer;
+	fbdev->info->screen_buffer = fbdev->buffer;
 	fbdev->info->screen_size = HT16K33_FB_SIZE;
 	fbdev->info->fix = ht16k33_fb_fix;
 	fbdev->info->var = ht16k33_fb_var;