dw_dmac: disable dma in optimal way in probe

The dw_dma_off call needs to have the all_chan_mask calculated. So, done this
calculations before the call. Moreover, remove duplicate code that masks the
DMA interrupts.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.linux@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>