i2c: rtl9300: introduce max length property to driver data

i2c: rtl9300: introduce max length property to driver data

In RTL9607C i2c controller, theoretical maximum the data length
can be is 4 bytes as opposed to 16 bytes on rtl9300 and rtl9310.

Introduce a new property to the driver data struct for that.
Adjust if statement in prepare_xfer function to follow that new
property instead of the hardcoded value.

Signed-off-by: Rustam Adilov <adilov@disroot.org>
Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260401180648.337834-3-adilov@disroot.org