drm: hdlcd: Don't depend on VSYNC interrupt when setting new framebuffer.

drm: hdlcd: Don't depend on VSYNC interrupt when setting new framebuffer.

VSYNC state is influenced by the DRM framework and cannot be relied
on when setting a new framebuffer base address and synchronising with
the hardware. Use the DMA_END interrupt as it is a more reliable way
of signaling the end of frame utilisation.

Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>