Build: Merge tfm_partition_defs into tfm_config

The purpose of tfm_partition_defs is to expose the partition related
compile definitions, which can easily be covered by tfm_config.
So merge tfm_partition_defs into tfm_config to reduce the number of
CMake targets.

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I8ac9983ece670383183459554c9a22e1e8e22d66
diff --git a/toolchain_GNUARM.cmake b/toolchain_GNUARM.cmake
index 59d767e..1c4d3c7 100644
--- a/toolchain_GNUARM.cmake
+++ b/toolchain_GNUARM.cmake
@@ -258,7 +258,7 @@
     target_link_libraries(${target}_scatter
         platform_region_defs
         psa_interface
-        tfm_partition_defs
+        tfm_config
     )
 
     target_compile_options(${target}_scatter