regulator: max77686: Add suspend disable for some LDOs

Some LDOs of Maxim 77686 PMIC support disabling during system suspend
(LDO{2,6,7,8,10,11,12,14,15,16}). This was already implemented as part
of set_suspend_mode function. In that case the mode was one of:
 - disable,
 - normal mode,
 - low power mode.
However there are no bindings for setting the mode during suspend.

Add suspend disable for LDO regulators supporting this. Re-use existing
max77686_buck_set_suspend_disable() function. This helps reducing
energy consumption during system sleep.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>