This is the same issue fixed in commit dcf5341f

 ("ARM: dts:
sun8i-q8-common: Do not set constraints on dc1sw regulator").
Commit message copied:

dc1sw is an on/off only regulator and as such it cannot have constraints.

This is a limitation of the kernel regulator implementation which resolves
supplies on the first regulator_get(), which is done after applying
constraints, and applying the constrains will fail because it calls
_regulator_get_voltage() and _regulator_do_set_voltage() both of which
will fail on a switch regulator when there is no supply (yet).

This causes registering of all axp22x regulators to fail with the
following errors:

[    1.395249] vcc-lcd: failed to get the current voltage(-22)
[    1.405131] axp20x-regulator axp20x-regulator: Failed to register dc1sw
[    1.412436] axp20x-regulator: probe of axp20x-regulator failed with error -22

This commit removes the constrains on dc1sw / vcc-lcd fixing this problem.
Note that dcdc1 itself is contrained to the exact same values, so this
does not change anything.

Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Cc: <stable@vger.kernel.org> # 4.6
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Olof Johansson <olof@lixom.net>