drm/amd/pm: add missing ->fini_microcode interface for Sienna Cichlid

stable inclusion
from stable-v5.10.141
commit 60d522f317078381ff8a3599fe808f96fc256cd5
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I685FC

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=60d522f317078381ff8a3599fe808f96fc256cd5



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[ Upstream commit 0a2d922a ]

To avoid any potential memory leak.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com>