Build: Use TFM_LIB_MODEL in CMake Configurations

The new TFM_LIB_MODEL config is introduced to divide library and IPC
model. The TFM_PSA_API is not a user configuration anymore.

This patch uses TFM_LIB_MODEL instead of TFM_PSA_API in CMake
Configurations.

Note: The substitution is only required for "Config Type" CMake files.

Change-Id: I264c181712151728c12a78b486a714f7f4fe6e57
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
diff --git a/test/config/set_config.cmake b/test/config/set_config.cmake
index 87a2bf2..629df30 100644
--- a/test/config/set_config.cmake
+++ b/test/config/set_config.cmake
@@ -51,7 +51,7 @@
     set(TEST_S_AUDIT            OFF        CACHE BOOL      "Whether to build S regression Audit log tests")
 endif()
 
-if (NOT TFM_PSA_API)
+if (TFM_LIB_MODEL)
     set(TEST_NS_IPC             OFF        CACHE BOOL      "Whether to build NS regression IPC tests")
     set(TEST_S_IPC              OFF        CACHE BOOL      "Whether to build S regression IPC tests")