Fix the format used by ThreadBase::toAudioPortConfig

Since 'toAudioPortConfig' is used to communicate to the HAL,
the emitted port config specification must use the HAL
audio format, not the processing format. This is consistent
with use of the 'format()' getter in other code, as it
also returns the HAL format.

Bug: 298175108
Test: atest audiosystem_tests
Change-Id: I4a09a9f312a1415f7dcb7381a8198a9d60467388