regulator: lp87565: Simplify lp87565_buck_set_ramp_delay

Use rdev->regmap/&rdev->dev instead of lp87565->regmap/lp87565->dev.
In additional, the lp87565->dev actually is the parent mfd device,
so the dev_err message is misleading here with lp87565->dev.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20190908035720.17748-1-axel.lin@ingics.com


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