spi: imx: Fix cleanup in remove and convert to

Merge series from Uwe Kleine-König <u.kleine-koenig@pengutronix.de>:

This small series converts the spi-imx driver to .remove_new(). The
motivation for this tree-wide effort are drivers that don't properly
cleanup and return an error code. This is broken as this results in
resource leaks. The spi-imx driver is such a driver. The idea is that if
the remove callback returns void it's obvious that an early error return
is wrong.