device_cgroup: Fix kernel-doc warnings in device_cgroup

Fix kernel-doc warnings in device_cgroup:

security/device_cgroup.c:835: warning: Excess function parameter
'dev_cgroup' description in 'devcgroup_legacy_check_permission'.

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>