drm/pl111: Do not use deprecated drm_driver.{enable|disable)_vblank

Do not use deprecated drm_driver.{enable|disable)_vblank callbacks,
but use drm_simple_kms_helpe's pipe callbacks instead.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Tested-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1518425574-32671-5-git-send-email-andr2000@gmail.com

drivers/gpu/drm/pl111/pl111_drm.h

@@ -79,8 +79,6 @@ struct pl111_drm_dev_private {
 };
 
 int pl111_display_init(struct drm_device *dev);
-int pl111_enable_vblank(struct drm_device *drm, unsigned int crtc);
-void pl111_disable_vblank(struct drm_device *drm, unsigned int crtc);
 irqreturn_t pl111_irq(int irq, void *data);
 int pl111_debugfs_init(struct drm_minor *minor);