Device will be removed from dev_list when refcount reaches 0, so the
dev_mutex must be locked before decreasing reference otherwise there's
a race where this device is still in dev_list with refcount 0 which will
assert or crash in amdgpu_device_initialize trying to use this device
instead of creating new one.
Fixes issue reported in https://gitlab.freedesktop.org/drm/amd/-/issues/2156#note_2268110
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
c8f327ce9c