sgm775: Fix build fail for TSP support on sgm775

Fixed the path to a source file specified in tsp makefile
Created a platform specific tsp makefile

Change-Id: I89565127c67eff510e48e21fd450af4c3088c2d4
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
3 files changed