regulator: ab8500: Introduce aux5, aux6 regulators for AB8540

Introduce aux5, aux6 into ab8540 regulator framework.

Signed-off-by: Zhenhua HUANG <zhenhua.huang@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Maxime COQUELIN <maxime.coquelin@stericsson.com>
Reviewed-by: David PARIS <david.paris@stericsson.com>
Reviewed-by: Philippe LANGLAIS <philippe.langlais@stericsson.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>