fifo8: rename fifo8_pop_buf() to fifo8_peekpop_buf()

fifo8: rename fifo8_pop_buf() to fifo8_peekpop_buf()

The fifo8_pop_buf() function will soon also be used for peek
operations, so rename the function accordingly. Create a new
fifo8_pop_buf() wrapper function that can be used by existing
callers.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Octavian Purdila <tavip@google.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240828122258.928947-6-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>