media: i2c: ds90ub960: Protect alias_use_mask with a mutex

media: i2c: ds90ub960: Protect alias_use_mask with a mutex

The aliased_addrs list represents the occupation of an RX port's hardware
alias table. This list and the underlying hardware table are only accessed
in the attach/detach_client() callbacks.

These functions are only called from a bus notifier handler in i2c-atr.c,
which is always called with the notifier chain's semaphore held. This
indirectly prevents concurrent access to the aliased_addrs list.
However, more explicit and direct locking is preferable. Moreover, with the
introduction of dynamic address translation in a future patch, the
attach/detach_client() callbacks will be called from outside of the
notifier chain's read section.

Introduce a mutex to protect access to the aliased_addrs list and its
underlying hardware table.

Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
Acked-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>