keep lwip

Author: Sarthak-Shaha

scripts/setup/silabs/simplicity_sdk_keep_folders.txt

@@ -151,6 +151,7 @@ common_15_4
 devices
 freertos
 glib
+lwip
 openthread
 openthread_stack
 platform
@@ -161,4 +162,4 @@ segger
 security_mbedtls
 security_mbedtls_source
 security_se_manager
-util
+util