regulator: as3722: detect SD0 low-voltage mode

SD0 may operate in low-voltage mode, with a minimum of 0.41V
and a maximum of 1.5V.  This is indicated by bit 4 of FUSE7.

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: Vince Hsu <vinceh@nvidia.com>
broonie.e6264@m.evernote.com
Signed-off-by: Mark Brown <broonie@linaro.org>