linux-phytec-ti

remoteproc: add api for retrieving a rproc unique id

A new api, rproc_get_id(), is added to allow remoteproc/rpmsg clients
to be able to retrieve a fixed unique id associated with a rproc
device. Each of the rprocs is given an ida index as well, but this
is dynamic depending on the order rproc_alloc is called (probe order),
and also depends on what remote processor devices are instantiated.
This unique id needs to be supported for both DT and non-DT devices.
The platform device id or the remoteproc alias id are therefore
chosen for non-DT and DT devices respectively, with the assumption
that the remoteproc devices are created with known platform device
ids or alias ids in DT.

Signed-off-by: Suman Anna <s-anna@ti.com>