phy: qualcomm: Add Synopsys 28nm Hi-Speed USB PHY driver

Adds Qualcomm 28nm Hi-Speed USB PHY driver support. This PHY is usually
paired with Synopsys DWC3 USB controllers on Qualcomm SoCs.

The PHY can come in two flavours femtoPHY or picoPHY. This commit adds
support for the femtoPHY with the possibility of extending to the picoPHY
with additional future commits. Both PHYs are on a 28 nanometer process
node.

[bod: Updated qcom_snps_hsphy_set_mode to match new method signature
      Added disjunct on mode > 0
      Removed regulator_set_voltage() in favour of setting floor in dts
      Removed 'snps' and from driver name
      Extended commit log to mention femtoPHY and picoPHY for future
      reference.]

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Jorge Ramirez-Ortiz <jorge.ramirez.ortiz@gmail.com>
Cc: linux-arm-msm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>