RSE: enable UART TX/RX control for the NS code

An eRPC server running on the NS side needs access for TX/RX control.

Change-Id: Ifca797c7eeb975f3cfbbe3f8467c2033248080c9
Signed-off-by: David Vincze <david.vincze@arm.com>
diff --git a/platform/ext/target/arm/rse/common/ns/common.cmake b/platform/ext/target/arm/rse/common/ns/common.cmake
index bab5962..29c8e3c 100644
--- a/platform/ext/target/arm/rse/common/ns/common.cmake
+++ b/platform/ext/target/arm/rse/common/ns/common.cmake
@@ -40,6 +40,11 @@
         platform_region_defs
 )
 
+target_compile_definitions(platform_ns
+    PRIVATE
+        $<$<BOOL:${CONFIG_ENABLE_NS_UART_TX_RX_CONTROL}>:UART_TX_RX_CONTROL_ENABLED>
+)
+
 target_compile_definitions(platform_region_defs
     INTERFACE
         $<$<BOOL:${RSE_XIP}>:RSE_XIP>