spi: dw: Add DMA support to the DW SPI MMIO driver

spi: dw: Add DMA support to the DW SPI MMIO driver

Since the common code in the spi-dw-dma.c driver is ready to be used
by the MMIO driver and now provides a method to generically (on any
DT or ACPI-based platforms) retrieve the Tx/Rx DMA channel handlers,
we can use it and a set of the common DW SPI DMA callbacks to enable
DMA at least for generic "snps,dw-apb-ssi" and "snps,dwc-ssi-1.01a"
devices.

Co-developed-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Co-developed-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Signed-off-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org
Link: https://lore.kernel.org/r/20200529131205.31838-15-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>