regulator: fan53555: Fix missing slew_reg/mask/shift settings for FAN53526

The di->slew_reg/di->slew_mask/di->slew_shift was not set in current code,
fix it.

Fixes: f2a9eb97 ("regulator: fan53555: Add support for FAN53526")
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20210525124017.2550029-1-axel.lin@ingics.com


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