Update switch_core_media.c - Patch for #2226

[shaunjstokes]

We've found that the patch https://github.com/signalwire/freeswitch/pull/2582 has the side effect of causing calls that fail to negotiate the same codec as Leg A for Leg B to fail with SIP 488 INCOMPATIBLE_DESTINATION. That's not an option for us, we need backwards compatibility with other codecs.

Rather than apply this for all codecs it should only apply for Opus. Now calls using Opus and other codecs establish correctly on both legs, and there are no issues with codec negotiation when the codecs on Leg A and Leg B don't match.