UPSTREAM: regulator: core: Ensure we are at least in bounds for our constraints

UPSTREAM: regulator: core: Ensure we are at least in bounds for our constraints

Currently we only attempt to set the voltage during constraints
application if an exact voltage is specified.  Extend this so that if
the currently set voltage for the regulator is outside the bounds set in
constraints we will move the voltage to the nearest constraint, raising
to the minimum or lowering to the maximum as needed.  This ensures that
drivers can probe without the hardware being driven out of spec.

Reported-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Tested-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
(cherry picked from commit fa93fd4ecc9c58475abac6db93a797bff893bc16)

Change-Id: I3e3e60f2f93e971364a74f9735c362acaa59f512
Signed-off-by: David Wu <david.wu@rock-chips.com>