spi: cadence-quadspi: Add missing blank line in cqspi_request_mmap_dma()

Fix "WARNING: Missing a blank line after declarations" reported by
checkpatch.pl.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20220510115141.212779-2-abbotti@mev.co.uk


Signed-off-by: Mark Brown <broonie@kernel.org>