regulator: ab8500: Use regulator_list_voltage_linear for fixed voltage

regulator: ab8500: Use regulator_list_voltage_linear for fixed voltage

Both ab8500_regulator_mode_ops and ab8500_regulator_ops do not have volt_table
setting, thus we can not use regulator_list_voltage_table for them.
However, they have min_uV setting with n_voltages = 1, so use
regulator_list_voltage_linear instead.

Also remove setting set_voltage_time_sel for ab8500_regulator_mode_ops.
It is used only for fixed voltage, so it does not need to implement
set_voltage_time_sel.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>