spi: imx: Do not print an error when PIO is used

There are cases that DMA is not used and the driver gracefully
falls back to PIO mode.

Do not treat it like an error message and move it to debug level instead.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20200818223519.8737-1-festevam@gmail.com


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