feat(fwu): introduce FWU platform-specific functions declarations
feat(fwu): introduce FWU platform-specific functions declarations

Added FWU platform specific functions declarations in common
platform header.

Change-Id: I637e61753ea3dc7f7e7f3159ae1b43ab6780aef2
Signed-off-by: Manish V Badarkhe <d2342ad575f6bc1a5f5a5b89d6db0f72dd7e0e4c@arm.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware