spi: spi-imx: spi_imx_buf_rx_swap_u32(): fix sparse warning: use swab32s() instead...

spi: spi-imx: spi_imx_buf_rx_swap_u32(): fix sparse warning: use swab32s() instead of cpu_to_be32()

This patch fixes the following sparse warning by using a swab32s()
instead of a cpu_to_be32(). The driver is used on little endian
systems only and we really want to swap the bytes.

| drivers/spi/spi-imx.c:305:29: warning: incorrect type in assignment (different base types)
| drivers/spi/spi-imx.c:305:29:    expected unsigned int val
| drivers/spi/spi-imx.c:305:29:    got restricted __be32 [usertype]
| drivers/spi/spi-imx.c:361:21: warning: incorrect type in assignment (different base types)
| drivers/spi/spi-imx.c:361:21:    expected unsigned int [assigned] [usertype] val
| drivers/spi/spi-imx.c:361:21:    got restricted __be32 [usertype]

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/r/20220502175457.1977983-5-mkl@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>