USB: phy-msm-usb: Add support for pinctrl framework

As the newer targets will be using pinctrl framework for gpio
configuration, our drivers need to be compatible with both set of targets
the one which do not use pinctrl and one which do. Adding support for both
these cases. phy-msm driver can configure vddmin gpio.

Change-Id: I037bbb40651e256b3c92b475be6187b93ee61456
Signed-off-by: Tarun Gupta <tarung@codeaurora.org>