ASoC: stm32: i2s: fix 32 bits channel length without mclk

ASoC: stm32: i2s: fix 32 bits channel length without mclk

[ Upstream commit dbf20c5e31ec92cd25b0eeb563d46887f15f534d ]

Fix divider calculation in the case of 32 bits channel
configuration, when no master clock is used.

Fixes: 9836b1e79c97 ("ASoC: stm32: Add I2S driver")
Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Link: https://lore.kernel.org/r/20211117104404.3832-1-olivier.moysan@foss.st.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>