regulator: max77620: Initialize values for DT properties

If regulator DT node doesn't exist, its of_parse_cb callback
function isn't called. Then all values for DT properties are
filled with zero. This leads to wrong register update for
FPS and POK settings.

Signed-off-by: Jinyoung Park <jinyoungp@nvidia.com>
Signed-off-by: Mark Zhang <markz@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org