dw_dmac: rename DT related methods to reflect their belonging

Since we will have not only DT cases in future let's rename DT related methods
to reflect their belonging.

The rename was done as follows:
	struct dw_dma_filter_args	-> struct dw_dma_of_filter_args
	dw_dma_generic_filter()		-> dw_dma_of_filter()
	dw_dma_xlate()			-> dw_dma_of_xlate()
	dw_dma_id_table			-> dw_dma_of_id_table

There is no functional change.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>