dma-mapping: add i/o coherency support for 32bit

Add the I/O coherency support for devices that can issue a cache
coherent transactions.

Change-Id: I01b1dca4d72395df41ac5b882dcd3fd75a682b8c
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Signed-off-by: Vishwanath Raju K <vishk@codeaurora.org>