regulator: da9063: Fix get_mode() functions to read sleep field

get_mode() is used to retrieve the active mode state. Settings-A
config is used during active state, whilst Settings-B is for
suspend. This means we only need to check the sleep field of each
buck and LDO as that field solely relates to Settings-A config.

This change is a clone of the get_mode() update which was committed
as part of:
 - regulator: da9062: fix suspend_enable/disable preparation
   [a72865f0]

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Link: https://lore.kernel.org/r/20200324092516.60B5C3FB8D@swsrvapps-01.diasemi.com


Signed-off-by: Mark Brown <broonie@kernel.org>