Use libpsa in ts-demo

Modify the demo application to use the prebuilt PSA clients from
libpsa instead of directly building these.

Signed-off-by: Gabor Toth <gabor.toth2@arm.com>
Change-Id: Ib714c7ad901039c56ec6b021ff052b0329c79605
diff --git a/components/app/ts-demo/component.cmake b/components/app/ts-demo/component.cmake
index c4a7392..fe0f5fa 100644
--- a/components/app/ts-demo/component.cmake
+++ b/components/app/ts-demo/component.cmake
@@ -1,5 +1,5 @@
 #-------------------------------------------------------------------------------
-# Copyright (c) 2020, Arm Limited and Contributors. All rights reserved.
+# Copyright (c) 2020-2023, Arm Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -9,6 +9,6 @@
 endif()
 
 target_sources(${TGT} PRIVATE
-	"${CMAKE_CURRENT_LIST_DIR}/ts-demo.cpp"
+	"${CMAKE_CURRENT_LIST_DIR}/ts-demo.c"
 	)