dmaengine: dw: introduce block2bytes() and bytes2block()

The newly introduced helpers prepare driver to support new DMA controller
hardware.

While here, introduce DWC_CTLH_BLOCK_TS() macro as well.

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