i3c: dw: Turn DAT array entry into a struct

In an upcoming change, we will want to store additional data about the
devices we have in the data address table.

Change the type of the DAT entries into a struct, which currently just
has the address data.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/9dc0d9e2857e851a0cf04819df48e5d31921f83e.1680161823.git.jk@codeconstruct.com.au
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>