apbh_dma: return error value on timeout

When a timeout occurs, the return value is prepared but never returned.
Fix that.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Marek Vasut <marek.vasut@gmail.com>
Acked-by: Stefano Babic <sbabic@denx.de>