regulator: twl-regulator: fix n_voltages for twl6030 variable LDOs

The n_voltages initializer for the TWL6030_ADJUSTABLE_LDO macro is
off by one, causing the the highest supported voltage to be
unreachable.  Setting the machine constraints to only allow the
highest voltage causes errors:

machine_constraints_voltage: VAUX3_6030: unsupportable voltage constraints
twl_reg twl_reg.39: can't register VAUX3_6030, -22
twl_reg: probe of twl_reg.39 failed with error -22

This patch fixes the off by one error.  Tested by setting
VAUX3_6030 to 3.3V.

Signed-off-by: Colin Cross <ccross@android.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>