Audio VTS: Do not constrain implementation frameCount

The test was assuming Stream::getFrameCount() would return the
AudioConfig::frameCount used to create the stream, similarly
to the sampleRate or the channelMask.

Nevertheless this is not the case as the AudioConfig::frameCount
field is not to used by Stream::openOutputStream (nor Input) as
the buffer size is chosen by the HAL, not the framework.

Thus the test can not assume the frameCount chosen by the HAL and
must not test for a particular value.

Test: atest VtsHalAudioV4_0TargetTest
Bug: 116169974
Change-Id: Ibbf0825f540957e01e7c512d851cb9628991f4c4
Signed-off-by: Kevin Rocard <krocard@google.com>