drm/vc4: Fix clock source for VEC PixelValve on BCM2711

stable inclusion
from stable-5.10.51
commit 48c96d5bacc0fb87e6d516564ec3cee66f274c53
bugzilla: 175263 https://gitee.com/openeuler/kernel/issues/I4DT6F

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=48c96d5bacc0fb87e6d516564ec3cee66f274c53



--------------------------------

[ Upstream commit fc7a8abc ]

On the BCM2711 (Raspberry Pi 4), the VEC is actually connected to
output 2 of pixelvalve3.

NOTE: This contradicts the Broadcom docs, but has been empirically
tested and confirmed by Raspberry Pi firmware devs.

Signed-off-by: Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210520150344.273900-2-maxime@cerno.tech


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>