dma: dw: allow to stop in DW_DMA_SUSPENDED state

Allow DMA channel to be stopped even if it is in suspended state.
The current code in dw_dma_stop() supports this, but the recently
added early check for dw_dma_is_enabled() results in DMA stop
sequence to be skipped if the channel was in suspended state.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>