[rdkb][common][app][Refactor ccsp-wifi-agent bbappend]

[Description]
Refactor ccsp-wifi-agent bbappend
1. enable CONFIG_DFS flag

[Release-log]

diff --git a/recipes-ccsp/ccsp/ccsp-wifi-agent.bbappend b/recipes-ccsp/ccsp/ccsp-wifi-agent.bbappend
index 7c71fc0..da13fed 100644
--- a/recipes-ccsp/ccsp/ccsp-wifi-agent.bbappend
+++ b/recipes-ccsp/ccsp/ccsp-wifi-agent.bbappend
@@ -5,7 +5,7 @@
 LDFLAGS += " \
 	-lutopiautil \
 	   "
-CFLAGS_append = " -Wno-error -DWIFI_HAL_VERSION_3"
+CFLAGS_append = " -Wno-error -DWIFI_HAL_VERSION_3 -DCONFIG_DFS"
 
 #work around for wifi restart_flag=false, for meshagent synchroniztaion
 do_configure_prepend() {