drm: remove drm_vblank_no_hw_counter assignment from driver code

Core code already makes drm_driver.get_vblank_counter hook optional by
letting drm_vblank_no_hw_counter be the default implementation for the
function hook.  So the drm_vblank_no_hw_counter assignment in the driver
code becomes redundant and can be removed now.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Mali DP Maintainers <malidp@foss.arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Xinliang Liu <z.liuxinliang@hisilicon.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: CK Hu <ck.hu@mediatek.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Mark Yao <mark.yao@rock-chips.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Jyri Sarha <jsarha@ti.com>
Cc: Eric Anholt <eric@anholt.net>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Alexey Brodkin <abrodkin@synopsys.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1486458995-31018-3-git-send-email-shawnguo@kernel.org