spi: spi-imx: complete conversion from master -> controller

With patch:
| 8caab75f ("spi: Generalize SPI "master" to "controller"")
the SPI "master" was generalized to "controller". This patch completed
the conversion of the spi-imx driver by replacing the remaining
occurrences of master to controller.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/r/20220502175457.1977983-7-mkl@pengutronix.deSigned-off-by: Mark Brown <broonie@kernel.org>