drivers: mailbox: Fix all issues reported by sparse

commit 76591332a3d2394999d913374276ccc789f937ce from
https://github.com/nxp-auto-linux/linux



This fixes all issues reported by sparse. Most of them are related to
__iomem casts and reads. Some fixes required changes in the interface
between LLCE Mailbox and LLCE CAN core drivers.

Issue: ALB-9835
Signed-off-by: Ghennadi Procopciuc <ghennadi.procopciuc@nxp.com>
Signed-off-by: Zhantao Tang <zhantao.tang@windriver.com>