Match USB port ID on re-enumeration

When executing the RCM process, the Tegra device will be re-enumerated
on the USB bus once the miniloader is booted. This requires tegrarcm to
search for it again. In a system with multiple attached Tegra boards, all
being booted/shutdown in parallel, it is possible that the second call to
usb_open() will find a different Tegra device. Solve this issue by having
usb_open() record the exact physical USB port path of the device, and
match only that path on subsequent searches. This will be robust except in
the case where the device being operated on is physically unplugged and
replaced (not simply power-cycled) while tegrarcm is executing. This is
much less likely that the previous failure modes.

This feature also enables the next patch in this series.

Signed-off-by: Stephen Warren <swarren@nvidia.com>

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