drivers: i3c: specify start addr when searching for a free addr

For example, if a driver needed to reserve address before it does a
ENTDAA, it would need to get free address in a loop, but the get
free address func would return the same address everytime. It needs
the start address, which would be the last free address it go, to
be passed in to get the next free address.

Signed-off-by: Ryan McClelland <ryanmcclelland@meta.com>