dt-bindings: Add Qualcomm USB SuperSpeed PHY bindings

Binding description for Qualcomm's Synopsys 1.0.0 SuperSpeed PHY. This PHY
appears in a number of SoCs on various flavors of 20nm and 28nm nodes.

This commit adds information related to the 28nm node only.

Based on Sriharsha Allenki's <sallenki@codeaurora.org> original
definitions.

[bod: converted to yaml format]

Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Cc: Jorge Ramirez-Ortiz <jorge.ramirez.ortiz@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Jorge Ramirez-Ortiz <jorge.ramirez.ortiz@gmail.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Rob Herring <robh@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>