Add vblank irq handle.

v8: None.
v7:
- Fix irq flag "DRIVER_IRQF_SHARED" to "IRQF_SHARED".
v6: None.
v5: None.
v4: None.
v3:
- Remove hisi_get_crtc_from_index func.
- A few cleanup.
v2:
- Remove abtraction layer.
Signed-off-by: Xinliang Liu <xinliang.liu@linaro.org>
Signed-off-by: Xinwei Kong <kong.kongxinwei@hisilicon.com>