fbdev: lcdcfb: Register sysfs groups through driver core

[WHY]
   1. The driver forgot to call device_remove_file()
   in sh_mobile_lcdc_overlay_fb_unregister(), and there was
   no error handling when calling device_create_file() failed.

   2. This should probably use device_add_group() instead of
   individual files to simplify both creation and removal. [Arnd]

   3. The driver core can register and cleanup sysfs groups already.
   as commit 95cdd538 ("fbdev: efifb: Register sysfs groups
   through driver core").

[HOW]
   Register sysfs groups through driver core.

Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>
Signed-off-by: Helge Deller <deller@gmx.de>