spi: spi-qcom-qspi: Call dma_wmb() after setting up descriptors

spi: spi-qcom-qspi: Call dma_wmb() after setting up descriptors

After setting up dma descriptors and before initiaiting dma transfer, call
dma_wmb() to ensure all writes go through.
This doesn't fix any reported problem but is added for safety.

Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
Fixes: b5762d95607e ("spi: spi-qcom-qspi: Add DMA mode support")
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/1690285689-30233-4-git-send-email-quic_vnivarth@quicinc.com
Signed-off-by: Mark Brown <broonie@kernel.org>