spi: spi-fsl-spi: call spi_finalize_current_message() at the end

spi_finalize_current_message() shall be called once all
actions are finished, otherwise the last actions might
step over a newly started transfer.

Fixes: c592becb ("spi: fsl-(e)spi: migrate to generic master queueing")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>