ENGR00121069: MX51: Complete the constraints for the various regulators.

Completed intialization of mc13892 regulators. This was causing the
regulator API to leave many regulators enabled at boot and also print
error messages at boot.

Signed-off-by: Ranjani Vaidyanathan <Ranjani.Vaidyanathan@freescale.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>