dmaengine: dw-edma: Use non-atomic io-64 methods

Instead of splitting the 64-bits IOs up into two 32-bits ones it's
possible to use the already available non-atomic readq/writeq methods
implemented exactly for such cases. They are defined in the dedicated
header files io-64-nonatomic-lo-hi.h/io-64-nonatomic-hi-lo.h. So in case
if the 64-bits readq/writeq methods are unavailable on some platforms at
consideration, the corresponding drivers can have any of these headers
included and stop locally re-implementing the 64-bits IO accessors taking
into account the non-atomic nature of the included methods. Let's do that
in the DW eDMA driver too. Note by doing so we can discard the
CONFIG_64BIT config ifdefs from the code.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-By: Vinod Koul <vkoul@kernel.org>
[mani: fixed up while rebasing]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>