spi: fsl-espi: remove element status from struct fsl_espi_transfer

Use the return values of the functions in the call chain to transport
status information instead of using an element in struct
fsl_espi_transfer for this.

This is more in line with the general approach how to handle status
information and is one step further to eventually get rid of
struct fsl_espi_transfer completely.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>