tests: devicetree: add bits to test multi-bus nodes

This adds a few bits to the devicetree API tests for multi-bus
nodes where a bus can support multiple protocols. This uses
I3C as basis as I3C controller can support both I2C and I3C on
the same bus, while I2C controller cannot support both. So
this needs to make sure the correct bus macros are generated
if appropriate (and not generated if not needed).

Signed-off-by: Daniel Leung <daniel.leung@intel.com>