bridge_native_rtp.c: Minor code cleanups.

In native_rtp_bridge_compatible_check()

* Made one variable declaration per line.

* Extracted if test assignment to make the test easier to see.

* Made long if tests easier to see the combinatorial logic.

* Added bridge id to a couple debug messages.

Change-Id: I65bc5732aa7c9a2537f062f106fbea711cf2daad