util/fifo8: Rename fifo8_pop_buf() -> fifo8_pop_bufptr()

util/fifo8: Rename fifo8_pop_buf() -> fifo8_pop_bufptr()

Since fifo8_pop_buf() return a const buffer (which points
directly into the FIFO backing store). Rename it using the
'bufptr' suffix to better reflect that it is a pointer to
the internal buffer that is being returned. This will help
differentiate with methods *copying* the FIFO data.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20240722160745.67904-6-philmd@linaro.org>