[PATCH v4 3/3] i3c: add i3cdev module to expose i3c dev in /dev

[Sam Agazaryan]

> It is less confusing if it is all fixed up in one patch.  Fix the
> comment on actual_len.  Make all controller drivers use actual_len
> not len for returning the length of data read.  And fix up mctp-i3c too.

Yeah, agreed.

For v5 I can add a patch to the series that does the following:
1. Clarifies the actual_len field in kerneldocs in <linux/i3c/device.h>.
2. Updates all controller drivers to populate actual_len (and not len) on
   reads, building on Meagan's patch.
3. Updates mctp-i3c to use xfer.actual_len.

Thanks,
Sam