DMAEngine: sirf: add DMA pause/resume support

pause/resume are important for users like ALSA sound drivers,
this patches make the sirf prima2/marco support DMA commands
DMA_PAUSE and DMA_RESUME.

Signed-off-by: Barry Song <Baohua.Song@csr.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>