arch: arm: add wrapper around dmac_*

Lowlevel dma_* routines have been converted to use start and size
instead of start and end addresses. As a consequence, the name
of __dma_* routines has also been altered following the terminology
below:
area: takes a start and size
range: takes a start and end.

Add wrapper around dmac_* to be used by the __dma__* routines.

Change-Id: Ib976605b56a49fd21a72b40de84a629bf693888c
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>