ASoC: omap-mcbsp: Fix latency value calculation for pm_qos

[ Upstream commit dd2f52d8991af9fe0928d59ec502ba52be7bc38d ]

The latency number is in usec for the pm_qos. Correct the calculation to
give us the time in usec

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>