tests/unit: Strengthen FIFO8 tests

Replace reused bytes { 0x1, 0x2, 0x3, 0x4 } by { 0x9, 0xa, 0xb, 0xc }
to be sure a different value is overwritten.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20240906132909.78886-2-philmd@linaro.org>
1 file changed