tests: net: all: Make sure gratuitous ARP transmission is enabled

Add you config to the build-all net tests, to make sure everything build
properly.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>

Author: rlubos

tests/net/all/prj.conf

@@ -221,6 +221,7 @@ CONFIG_NET_ARP=y
 CONFIG_NET_ARP_TABLE_SIZE=3
 CONFIG_NET_ARP_LOG_LEVEL_DBG=y
 CONFIG_NET_ARP_GRATUITOUS=y
+CONFIG_NET_ARP_GRATUITOUS_TRANSMISSION=y
 
 # Logging
 CONFIG_NET_LOG=y