usb: phy: Add snapshot of phy-msm-ssusb driver

This is a snapshot of phy-msm-ssusb.c taken as of
msm-3.18 'commit 1514d9b155ed ("soc: qcom: bgrsb:
Add support to configure RSB on BG")'.

This change also fixes compilation issues:
1. Use reset framework for assert and deassert of
reset clocks.
2. Use regulator_set_load as regulator_set_optimum_mode
is not present anymore.
3. Add required phy flags definitions.

Change-Id: I2c9ef829c8e821ab3627a2557d4d1f80b74c7fac
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>