regulator: max597x: Remove the unneeded result variable

Return the value from regmap_write() 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/20220824074707.221159-1-ye.xingchen@zte.com.cn


Signed-off-by: Mark Brown <broonie@kernel.org>