drm: bridge: adv7511: Remove redundant null check before clk_disable_unprepare

[ Upstream commit 3fc5a284 ]

Because clk_disable_unprepare() already checked NULL clock parameter,
so the additional check is unnecessary, just remove them.

Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Stable-dep-of: 81adbd3f ("drm: adv7511: Fix use-after-free in adv7533_attach_dsi()")
Signed-off-by: Sasha Levin <sashal@kernel.org>