drm/amdgpu: add a missing lock for AMDGPU_SCHED

stable inclusion
from stable-v5.10.180
commit 7f497a9451d716d8e46a3907996151a23296d49b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8FC2O

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7f497a9451d716d8e46a3907996151a23296d49b



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[ Upstream commit 2397e3d8 ]

mgr->ctx_handles should be protected by mgr->lock.

v2: improve commit message
v3: add a Fixes tag

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Fixes: 52c6a62c ("drm/amdgpu: add interface for editing a foreign process's priority v3")
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>