mtd: spi-nor: cadence-quadspi: Handle probe deferral while requesting DMA channel

mtd: spi-nor: cadence-quadspi: Handle probe deferral while requesting DMA channel

[ Upstream commit 6ae9bf23828d11ed7bedb4aa1e25747fd93b3369 ]

dma_request_chan_by_mask() can throw EPROBE_DEFER if DMA provider
is not yet probed. Currently driver just falls back to using PIO mode
(which is less efficient) in this case. Instead return probe deferral
error as is so that driver will be re probed once DMA provider is
available.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Acked-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200601070444.16923-6-vigneshr@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Stable-dep-of: 2087e85bb66e ("spi: cadence-quadspi: fix suspend-resume implementations")
Signed-off-by: Sasha Levin <sashal@kernel.org>