spi: lpspi: Remove the unneeded result variable

Return the value pm_runtime_force_suspend() directly instead of storing
it in another redundant variable.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Link: https://lore.kernel.org/r/20220908010429.342875-1-ye.xingchen@zte.com.cn
Signed-off-by: Mark Brown <broonie@kernel.org>