ENGR00230167 MX6 regulator: enable and raise the voltage of USB 3p0 LDO

ENGR00230167 MX6 regulator: enable and raise the voltage of USB 3p0 LDO

The USB FS eye test will fail in MX6 board if the 3V USB phy LDO is not enabled.
Setting enable bit (bit-0) of LDO 3p0 will make 3p0 LDO to use bandgap output as
reference voltage, LDO output will be accurate. And HW team suggest that it is
better to raise the voltage of USB 3p0 phy LDO 3.2V to pass the USB compliance
testing.

- Implement vdd3p0 regulator enable and disable function to support
  enable and disable the LDO 3p0 regulator.
- Use regulator API to enable the USB 3p0 phy LDO and raise the LDO
  to 3.2V during system boot up. And disable the LDO before system
  enter suspend and enable the LDO again after system resume.

Signed-off-by: make shi <b15407@freescale.com>