regulator: tps65023: Fixes i2c configuration issues

Allow i2c core voltage adjustments by clearing CORE ADJ Allowed bit in CTRL2

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>