drm/amdgpu: Fix sdma v4 sw fini error

Fix sdma v4 sw fini error for sdma 4.2.2 to
solve the following general protection fault

[  +0.108196] general protection fault, probably for non-canonical
address 0xd5e5a4ae79d24a32: 0000 [#1] PREEMPT SMP PTI
[  +0.000018] RIP: 0010:free_fw_priv+0xd/0x70
[  +0.000022] Call Trace:
[  +0.000012]  <TASK>
[  +0.000011]  release_firmware+0x55/0x80
[  +0.000021]  amdgpu_ucode_release+0x11/0x20 [amdgpu]
[  +0.000415]  amdgpu_sdma_destroy_inst_ctx+0x4f/0x90 [amdgpu]
[  +0.000360]  sdma_v4_0_sw_fini+0xce/0x110 [amdgpu]

Signed-off-by: lyndonli <Lyndon.Li@amd.com>
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>