spi: mvebu: fix error handling for transfer problems
When a message transfer fails no further messages are transferred, but
the error value was not propagated to the caller.
Fixes: 5db1a578d6ed ("spi: add Marvell MVEBU SoC SPI driver")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>