spi: dw: Add SPI Rx-done wait method to DMA-based transfer

Having any data left in the Rx FIFO after the DMA engine claimed it has
finished all DMA transactions is an abnormal situation, since the DW SPI
controller driver expects to have all the data being fetched and placed
into the SPI Rx buffer at that moment. In case if that has happened we
hopefully assume that the DMA engine may still be doing the data fetching,
thus we give it sometime to finish. If after a short period of time the
data is still left in the Rx FIFO, the driver will give up waiting and
return an error indicating that the SPI controller/DMA engine must have
hung up or failed at some point of doing their duties.

Fixes: 7063c0d942a1 ("spi/dw_spi: add DMA support")
Co-developed-by: Georgy Vlasov <[email protected]>
Signed-off-by: Georgy Vlasov <[email protected]>
Signed-off-by: Serge Semin <[email protected]>
Cc: Ramil Zaripov <[email protected]>
Cc: Alexey Malahov <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Feng Tang <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>

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