tomoyo: Suppress RCU warning at list_for_each_entry_rcu().

tomoyo: Suppress RCU warning at list_for_each_entry_rcu().

BugLink: https://bugs.launchpad.net/bugs/1861085
[ Upstream commit 6bd5ce6089b561f5392460bfb654dea89356ab1b ]

John Garry has reported that allmodconfig kernel on arm64 causes flood of
"RCU-list traversed in non-reader section!!" warning. I don't know what
change caused this warning, but this warning is safe because TOMOYO uses
SRCU lock instead. Let's suppress this warning by explicitly telling that
the caller is holding SRCU lock.

Reported-and-tested-by: John Garry <john.garry@huawei.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>