mtd: rawnand: lpc32xx_slc: fail DMA transfer on completion timeout
lpc32xx_xmit_dma() waits for the DMA completion callback but ignores
wait_for_completion_timeout(). A timed out DMA transfer is therefore
unmapped and reported as successful to the NAND read/write path.
Return -ETIMEDOUT when the completion wait expires. Terminate the DMA
channel before unmapping the scatterlist so the timed out transfer cannot
continue to access the buffer after the error is returned.