kernel: hide kmod-pppox

The pppox module is a dependency of pppoe/pptp/pppol2tp and does not
have a separate Kconfig symbol.

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
Link: openwrt/openwrt#23077
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

Author: LGA1150

package/kernel/linux/modules/netsupport.mk

@@ -605,7 +605,7 @@ define KernelPackage/pppox
   SUBMENU:=$(NETWORK_SUPPORT_MENU)
   TITLE:=PPPoX helper
   DEPENDS:=kmod-ppp
-  KCONFIG:=CONFIG_PPPOE
+  HIDDEN:=1
   FILES:=$(LINUX_DIR)/drivers/net/ppp/pppox.ko
 endef