sched/deadline: Comment sched_dl_entity::dl_server variable

sched/deadline: Comment sched_dl_entity::dl_server variable

commit f23c042ce34ba265cf3129d530702b5d218e3f4b upstream.

Add an explanation for the newly added variable.

Fixes: 63ba8422f876 ("sched/deadline: Introduce deadline servers")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/147f7aa8cb8fd925f36aa8059af6a35aad08b45a.1716811044.git.bristot@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>