drm/fb-helper: Remove unused inline function drm_fb_helper_defio_init()

Since commit 8e86dee02253 ("drm/fb-helper: Remove drm_fb_helper_defio_init() and update docs")
this inline helper not used anymore.

Fixes: 8e86dee02253 ("drm/fb-helper: Remove drm_fb_helper_defio_init() and update docs")
Signed-off-by: YueHaibing <[e-mail]>
Reviewed-by: Thomas Zimmermann <[e-mail]>
Signed-off-by: Thomas Zimmermann <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

include/drm/drm_fb_helper.h

···
 {
 }
 
-static inline int drm_fb_helper_defio_init(struct drm_fb_helper *fb_helper)
-{
-	return -ENODEV;
-}
-
 static inline void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper,
 					     bool suspend)
 {