ASoC: atmel_ssc_dai: fix spelling mistake: "Stoping" -> "Stopping"

Trivial fix to spelling mistake in pr_debug message text

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>