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_configs.py b/build_helper/build_helper_configs.py
index 236a3dc..255894e 100755
--- a/build_helper/build_helper_configs.py
+++ b/build_helper/build_helper_configs.py
@@ -451,7 +451,7 @@
                 "with_ns":          [True],
                 "profile":          [""],
                 "partition_ps":     ["ON"],
-                "extra_params":     ["FPSOFT", "FPHARD", "FPHARD_LOFF"]
+                "extra_params":     ["FPSOFT", "FPHARD", "FPHARD, LZOFF"]
                 },
                 "common_params": _common_tfm_builder_cfg,
                 "invalid": _common_tfm_invalid_configs + []
@@ -725,7 +725,7 @@
                 "with_ns":          [False],
                 "profile":          [""],
                 "partition_ps":     ["ON"],
-                "extra_params":     ["FVP", "FPGA"]
+                "extra_params":     ["S_PS_OFF, FVP", "FPGA"]
                 },
                 "common_params": _common_tfm_builder_cfg,
                 "invalid": _common_tfm_invalid_configs + []