regulator: pca9450: Clear PRESET_EN bit to fix BUCK1/2/3 voltage setting

The driver uses the DVS registers PCA9450_REG_BUCKxOUT_DVS0 to set the
voltage for the buck regulators 1, 2 and 3. This has no effect as the
PRESET_EN bit is set by default and therefore the preset values are used
instead, which are set to 850 mV.

To fix this we clear the PRESET_EN bit at time of initialization.

Fixes: 0935ff5f

 ("regulator: pca9450: add pca9450 pmic driver")
Cc: <stable@vger.kernel.org>
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Link: https://lore.kernel.org/r/20210222115229.166620-1-frieder.schrempf@kontron.de
Signed-off-by: Mark Brown <broonie@kernel.org>