regulator: act8865: Specify fixed voltage of 3.3V for ACT8600's REG9

The documentation lists both 1.8V and 3.3V for this regulator output,
but 3.3V is mentioned more often and also matches what JZ4770 and
JZ4780 expect as an input.

Note that the voltage of REG9 is not programmable, so this commit only
changes the voltage reported in sysfs and debugfs, not the actual
output voltage of the hardware.

Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>
Signed-off-by: Mark Brown <broonie@kernel.org>