[rdkb][common][app][Refactor xl2tpd bbapend]

[Description]
Refactor xl2tpd bbapend
1. add compile flag align to openwrt
2. support ppp over l2tp, buildin pppol2tp.so

[Release-log]

diff --git a/recipes-connectivity/xl2tpd/xl2tpd_%.bbappend b/recipes-connectivity/xl2tpd/xl2tpd_%.bbappend
index 240adfd..76b163d 100644
--- a/recipes-connectivity/xl2tpd/xl2tpd_%.bbappend
+++ b/recipes-connectivity/xl2tpd/xl2tpd_%.bbappend
@@ -1,4 +1,9 @@
 SRC_URI_remove = "git://github.com/xelerance/xl2tpd.git"
 SRC_URI += "git://github.com/xelerance/xl2tpd.git;branch=master;protocol=https"
 SRCREV = "1ef2a025981223c1e16fc833bef226c86ff8c295"
-UPSTREAM_CHECK_URI = "https://github.com/xelerance/xl2tpd/releases"
\ No newline at end of file
+UPSTREAM_CHECK_URI = "https://github.com/xelerance/xl2tpd/releases"
+
+
+CFLAGS_append += " -DUSE_KERNEL -DDEBUG_PPPD -DTRUST_PPPD_TO_DIE -DIP_ALLOCATION -DSANITY"
+RDEPENDS_${PN} += "ppp"
+RRECOMMENDS_${PN} += " ppp-l2tp"
\ No newline at end of file