Include if_pppolac.h and if_pppopns.h into header-y target

This is required to pass the headers_check

Change-Id: Ic4c773973278cbdf1cb4eb66473826cb96ccbfb3
Signed-off-by: Andrey Konovalov <andrey.konovalov@linaro.org>
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index 3c9b616..c5a9cae 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -183,6 +183,8 @@
 header-y += if_ppp.h
 header-y += if_pppol2tp.h
 header-y += if_pppox.h
+header-y += if_pppolac.h
+header-y += if_pppopns.h
 header-y += if_slip.h
 header-y += if_strip.h
 header-y += if_team.h