Build: Support multi params in 'extra_params'

This patch extend 'extra_params' in build helper to support multiple
extra params in one config. Params are seperated by ', '.

For example, for a config with both FPHARD and LZOFF enabled,
extra_params can be set as "FPHARD, LZOFF". Then the build helper
will append the configs in the build command generated automatically.

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I645284c4ef37d47feb5e31fe093d67a446778c5a
diff --git a/build_helper/build_helper_config_maps.py b/build_helper/build_helper_config_maps.py
index 1651c0b..009fdd7 100644
--- a/build_helper/build_helper_config_maps.py
+++ b/build_helper/build_helper_config_maps.py
@@ -65,9 +65,7 @@
     "FPSOFT"       : "-DCONFIG_TFM_FP=soft ",
     "FPHARD"       : ("-DCONFIG_TFM_FP=hard "
                       "-DTEST_S_FPU=ON -DTEST_NS_FPU=ON "),
-    "FPHARD_LOFF"  : ("-DCONFIG_TFM_FP=hard "
-                      "-DCONFIG_TFM_LAZY_STACKING=OFF "
-                      "-DTEST_S_FPU=ON -DTEST_NS_FPU=ON "),
+    "LZOFF"        : "-DCONFIG_TFM_LAZY_STACKING=OFF ",
     # SFN
     "SFN"          : "-DCONFIG_TFM_SPM_BACKEND=SFN ",
     # CC Driver
@@ -80,4 +78,5 @@
     # Corstone1000 support
     "FVP"          : "-DPLATFORM_IS_FVP=True ",
     "FPGA"         : "-DPLATFORM_IS_FVP=False ",
+    "S_PS_OFF"     : "-DTEST_S_PS=OFF ",
 }