drm/amd/display: Get LTTPR IEEE OUI/Device ID From Closest LTTPR To Host

[WHY]
These fields are read for the explicit purpose of detecting embedded LTTPRs
(i.e. between host ASIC and the user-facing port), and thus need to
calculate the correct DPCD address offset based on LTTPR count to target
the appropriate LTTPR's DPCD register space with these queries.

[HOW]
Cascaded LTTPRs in a link each snoop and increment LTTPR count when queried
via DPCD read, so an LTTPR embedded in a source device (e.g. USB4 port on a
laptop) will always be addressible using the max LTTPR count seen by the
host. Therefore we simply need to use a recently added helper function to
calculate the correct DPCD address to target potentially embedded LTTPRs
based on the received LTTPR count.

Cc: Mario Limonciello <[email protected]>
Cc: Alex Deucher <[email protected]>
Reviewed-by: Wenjing Liu <[email protected]>
Signed-off-by: Michael Strauss <[email protected]>
Signed-off-by: Alex Hung <[email protected]>
Tested-by: Daniel Wheeler <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
(cherry picked from commit 791897f5c77a2a65d0e500be4743af2ddf6eb061)
Cc: [email protected]

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