tcpdump: Fix buffer overrun in ATM OAM printing (Coverity)
Fix buffer overrun in oam_print() when printing ATM OAM fields.
The previous code iterated over the loopback_id, source_id, and failure_location
arrays and, on certain indexes, printed a 16-bit value starting at that index.
This could result in a buffer overrun on the last iteration, as it could read
past the end of the array.
Update the loops to increment by 2 and only access valid 16-bit aligned elements,
ensuring no out-of-bounds access occurs.
This change was made to address issues reported by Coverity static analysis.
No functional change except improved safety.