spi: imx: terminate RX DMA transaction in case of TX DMA timeout

Not only TX DMA should be terminated, but RX DMA also. It's required
to avoid accidential DMA memory writes from RX DMA channel and properly
terminate transaction.

Signed-off-by: Anton Bondarenko <anton.bondarenko.sama@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>