drivers/regulator: remove redundant ret variable

Return value from twlreg_write() directly instead
of taking this in another redundant variable.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Link: https://lore.kernel.org/r/20211213021655.435423-1-chi.minghao@zte.com.cn


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