Currently if targets support ESOC there would almost certainly
only be a single instance of an external modem. Hence we can
simplify the esoc_link check accordingly without needing to do
a loop and grep. Choosing the external modem composition simply
depends on whether esoc_name is present.
Change-Id: Ib47e34fd31c3745a0c7b3568968f6f36681c98e7