drm/amd/display: FEC check in timing validation

stable inclusion
from stable-v5.10.112
commit 6906e05cf3ad2cfe704eda003de59aa0cb89b291
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=6906e05cf3ad2cfe704eda003de59aa0cb89b291



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[ Upstream commit 7d56a154 ]

[Why]
disable/enable leads FEC mismatch between hw/sw FEC state.

[How]
check FEC status to fastboot on/off.

Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Chiawen Huang <chiawen.huang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@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>