this patch adds PM ops entries in sirf-dma drivers, so that this
driver can support suspend/resume, hibernation and runtime PM.

while suspending, sirf-dma will lose all registers, so we save
them at suspend and restore in resume for active channels.
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Rongjun Ying <Rongjun.Ying@csr.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>