spi: dw: Add Tx/Rx DMA properties

Since commit 22d48ad ("spi: dw: Add Elkhart Lake PSE DMA support")
the spi-dw-mid.c module supports a platform DMA engine handling the DW APB
SSI controller requests. Lets alter the DW SPI bindings file to accept the
Rx and Tx DMA line specifiers.

Signed-off-by: Serge Semin <[email protected]>
Cc: Georgy Vlasov <[email protected]>
Cc: Ramil Zaripov <[email protected]>
Cc: Alexey Malahov <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Allison Randal <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Gareth Williams <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: fancer

Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt

@@ -23,6 +23,8 @@ Optional properties:
 - num-cs : The number of chipselects. If omitted, this will default to 4.
 - reg-io-width : The I/O register width (in bytes) implemented by this
   device.  Supported values are 2 or 4 (the default).
+- dmas : Phandle + identifiers of Tx and Rx DMA channels.
+- dma-names : Contains the names of the DMA channels. Must be "tx" and "rx".
 
 Child nodes as per the generic SPI binding.