ASoC: fsi: don't reschedule DMA from an atomic context

commit 57451e437796548d658d03c2c4aab659eafcd799 upstream.

shdma doesn't support transfer re-scheduling or triggering from callbacks
or from atomic context. The fsi driver issues DMA transfers from a tasklet
context, which is a bug. To fix it convert tasklet to a work.

Reported-by: Do Q.Thang <dq-thang@jinso.co.jp>
Tested-by: Do Q.Thang <dq-thang@jinso.co.jp>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>