spi: imx: Simplify logic in spi_imx_push()

For each usage of fifo_words it is clear if ->dynamic_burst is true or
not. This can be used to simplify the function a bit.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20210716173927.2050620-1-u.kleine-koenig@pengutronix.de


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