hid/hid-picolcd_fb: 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/20230428122452.4856-4-tzimmermann@suse.de

drivers/hid/hid-picolcd_fb.c

@@ -221,7 +221,7 @@ int picolcd_fb_reset(struct picolcd_data *data, int clear)
 	return 0;
 }
 
-/* Update fb_vbitmap from the screen_base and send changed tiles to device */
+/* Update fb_vbitmap from the screen_buffer and send changed tiles to device */
 static void picolcd_fb_update(struct fb_info *info)
 {
 	int chip, tile, n;
@@ -541,7 +541,7 @@ int picolcd_init_framebuffer(struct picolcd_data *data)
 		dev_err(dev, "can't get a free page for framebuffer\n");
 		goto err_nomem;
 	}
-	info->screen_base = (char __force __iomem *)fbdata->bitmap;
+	info->screen_buffer = fbdata->bitmap;
 	info->fix.smem_start = (unsigned long)fbdata->bitmap;
 	memset(fbdata->vbitmap, 0xff, PICOLCDFB_SIZE);
 	data->fb_info = info;