This allow to build with single FIFO for devices with multiple channels.
Having just one FIFO greatly reduces time needed to feed endpoint.
This change also allows to have one FIFO with 24 bit samples that
is not rounded up to 32 bit elements.
CFG_TUD_AUDIO_RX_ITEMSIZE and CFG_TUD_AUDIO_TX_ITEMSIZE can be manually
defined. This allows to use FIFO more efficiently when 24 bits samples
are already using 3 bytes, in this case there is no need to put them
into FIFO one by one.
For 8, 16, 32 bits samples size efficient FIFO access is always used
when single FIFO is selected.
This also changes FIFO element size to 1, FIFO usage was confusing
in some place it treated content as byte base in other it looked like
ITEM size is to be used. Also bufsize that in most (maybe all) cases
was really meaning item count.
bufsize now mean buffer size in bytes so there is no confusion.
Having just inline keyword for function specified in header
may not be enough to generate code for function.
Adding static solves this problem.
static inline is used in all other inline functions in TinyUSB.
This is helpful if you have already encoded audio data and want an
efficient way to send it. However, this approach is NOT THREADSAFE so
far and works realiably ONLY IF tud_audio_n_write_ep_in_buffer() is NOT
called form an interrupt!
