Add ncid to CellLocation in CellIdentityNr

Update GsmCellLocation documentation for NR case. Since the NR cell ID
is 36 bits and can't fit into the 32-bit field in GsmCellLocation,
return -1 for the CID.

Test: atest CellIdentityNrTest
Bug: 166514842
Change-Id: Ib894e83900b590c11221502ad039781cea5b571c