regulator: pf8x00: set ramp_delay for bucks

This patch sets ramp_delay for bucks to the max value given by the
datasheet.

Signed-off-by: Christoph Fritz <chf.fritz@googlemail.com>
Reviewed-by: Adrien Grassein <adrien.grassein@gmail.com>
Link: https://lore.kernel.org/r/60d8eb8feefd26380cc9c6503f835e569be90465.camel@googlemail.com


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