dmaengine: at_hdmac: add wrappers for testing channel state

Cyclic property and paused state are encoded as bits in the channel status
bitfield. Tests of those bits are wrapped in convenient helper functions.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>