cnss: Add internal modem SSR registration support

Modem could be external or internal on different platforms.
Current implementation of SSR registration is based on external
modem that gets modem name from esoc node in DT file, which is
not applicable to internal modem.
Add support for internal modem SSR registration.

Change-Id: Ifd0921f1113cd85fb2ba87e278b3406b90af25e1
CRs-Fixed: 641357
Signed-off-by: Yuanyuan Liu <yuanliu@codeaurora.org>