PLDM: Restrain from adding duplicate TL PDRs

This commit inhibits adding the duplicate terminus locator PDRs
to the repo. When the PDRs are removed based on the
terminus handle, the terminus locator PDR info is also
deleted from the map.

Tested with the normal poweron.

Change-Id: Ib973a41dc42324f9b5453a5f1a6592dc306729ff
Signed-off-by: Pavithra Barithaya <pavithra.b@ibm.com>