spi: fsl-lpspi: use wait_for_completion_timeout() while waiting transfer done

It's a potential problem to use wait_for_completion() because the
completion condition may never come. Thus, it's better to repalce
wait_for_completion() with wait_for_completion_timeout().

Signed-off-by: Gao Pan <pandy.gao@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>