drm/amdgpu/vcn: improve vcn dpg stop procedure

stable inclusion
from stable-v5.10.112
commit e5afacc826a80cd82ac3f9eb26bc80e45cd14c20
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5HL0X

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5afacc826a80cd82ac3f9eb26bc80e45cd14c20



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[ Upstream commit 6ea239ad ]

Prior to disabling dpg, VCN need unpausing dpg mode, or VCN will hang in
S3 resuming.

Reviewed-by: James Zhu <James.Zhu@amd.com>
Signed-off-by: Tianci Yin <tianci.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>