phy: tegra: xusb: Add Tegra186 support

Add support for the XUSB pad controller found on Tegra186 SoCs. It is
mostly similar to the same IP found on earlier chips, but the number of
pads exposed differs, as do the programming sequences.

Note that the DVDD_PEX, DVDD_PEX_PLL, HVDD_PEX and HVDD_PEX_PLL power
supplies of the XUSB pad controller require strict power sequencing and
are therefore controlled by the PMIC on Tegra186.

Signed-off-by: JC Kuo <jckuo@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
[dan.carpenter@oracle.com: Fix testing the wrong variable in probe()]
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
[yuehaibing@huawei.com: Make two functions static to fix sparse warning]
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>