phy: tegra: xusb: Add Tegra210 lane_iddq operation

As per Tegra210 TRM, before changing lane assignments, driver should
keep lanes in IDDQ and sleep state; after changing lane assignments,
driver should bring lanes out of IDDQ.
This commit implements the required operations.

Signed-off-by: JC Kuo <jckuo@nvidia.com>
Acked-By: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>