drm/amdgpu: Unlock a mutex before destroying it

drm/amdgpu: Unlock a mutex before destroying it

Mutexes must be unlocked before these are destroyed. This has been detected
by the Clang thread-safety analyzer.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Yang Wang <kevinyang.wang@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Fixes: f5e4cc8461c4 ("drm/amdgpu: implement RAS ACA driver framework")
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>