ppp: Remove already applied patch

This patch was already applied upstream and not needed here.

Fixes: 06403981e1 ("ppp: update to version 2.4.7.git-2019-05-06")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

package/network/services/ppp/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=ppp
-PKG_RELEASE:=5
+PKG_RELEASE:=6
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://github.com/paulusmack/ppp

package/network/services/ppp/patches/540-save-pppol2tp_fd_str.patch

@@ -1,13 +0,0 @@
---- a/pppd/plugins/pppol2tp/pppol2tp.c
-+++ b/pppd/plugins/pppol2tp/pppol2tp.c
-@@ -152,6 +152,10 @@ static int setdevname_pppol2tp(char **ar
- 	if (pppol2tp_fd_str == NULL)
- 		novm("PPPoL2TP FD");
- 
-+	pppol2tp_fd_str = strdup(*argv);
-+	if (pppol2tp_fd_str == NULL)
-+		novm("PPPoL2TP FD");
-+
- 	/* Setup option defaults. Compression options are disabled! */
- 
- 	modem = 0;