dsp: Set dma_mask to accept 64 bit dma address

We do not set the dma_mask so by default it only
accepts 32bit dma address. setting the dma_mask to
DMA_BIT_MASK(64) makes it accept 64 bit dma address
as well

Change-Id: I3c5dc78e69432f261bee26bf9e0d8d097bc16d09
Signed-off-by: Huicheng Liu <huicliu@codeaurora.org>