Build: Fix BL2 config in ConfigRegressionTfmLevel3.cmake

Change-Id: Iba827776797da72d21f2afc705be7fd937bf7598
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
diff --git a/ConfigRegressionTfmLevel3.cmake b/ConfigRegressionTfmLevel3.cmake
index 43a1c29..544567e 100644
--- a/ConfigRegressionTfmLevel3.cmake
+++ b/ConfigRegressionTfmLevel3.cmake
@@ -33,7 +33,16 @@
 set (TFM_LVL 3)
 
 #BL2 bootloader(MCUBoot) related settings
-set (BL2 True)
-set (MCUBOOT_NO_SWAP False)
+if(NOT DEFINED BL2)
+	set(BL2 True)
+endif()
+
+if(NOT DEFINED MCUBOOT_NO_SWAP)
+	set(MCUBOOT_NO_SWAP False)
+endif()
+
+if(NOT DEFINED MCUBOOT_RAM_LOADING)
+	set(MCUBOOT_RAM_LOADING False)
+endif()
 
 include ("${CMAKE_CURRENT_LIST_DIR}/CommonConfig.cmake")