Revert "dmaengine: omap-dma: Prevent race between vchan_complete() and terminate_all"

This reverts commit 28b39b51.
In non-RT kernel, this will cause a deadlock if omap_dma_terminate_all() is
called from the dma tasklet.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>