xdc: allow GTPE2_CHANNEL to have IO_LOC_PAIRS
xdc: allow GTPE2_CHANNEL to have IO_LOC_PAIRS

The GTPE2_CHANNEL does not have intermediate buffers to the IOPADs.
Therefore, it is necessary to allow it to have IO_LOC_PAIRS attributes
to generate correct placement constraints based on the IO signals
locations.

Signed-off-by: Alessandro Comodi <622632e70fd6771cf2cd943f69e5e51ab66adef8@antmicro.com>

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