i2c: i801: Annotate apanel_addr as __ro_after_init

[ Upstream commit 355b1513b1e97b6cef84b786c6480325dfd3753d ]

Annotate this variable as __ro_after_init to protect it from being
overwritten later.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 1a1f7053437d0f27534ecc9ec7e5d441c082b81c)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>