msm: ipa4: Adding changes to support load new GSI FW

Lito and Lagoon targets sharing same lunch option but
using different signing images, adding support
to load specific FW image to based on DTSI entry.

Change-Id: I468378fa163255a1ae8b0f7f2bb9726e7b656bd6
Signed-off-by: Ashok Vuyyuru <avuyyuru@codeaurora.org>