busybox 1.20.x: add if-post-up.d and if-pre-down.d to device table

Busybox 1.20.0 add functionality to execute scripts from if-post-up.d
and if-pre-down.d, so add the missing directories to the device table to
get them created and avoid unnecessary warnings if not.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

target/generic/device_table.txt

@@ -14,7 +14,9 @@
 /etc/passwd				f	644	0	0	-	-	-	-	-
 /etc/network/if-up.d			d	755	0	0	-	-	-	-	-
 /etc/network/if-pre-up.d		d	755	0	0	-	-	-	-	-
+/etc/network/if-post-up.d		d	755	0	0	-	-	-	-	-
 /etc/network/if-down.d			d	755	0	0	-	-	-	-	-
+/etc/network/if-pre-down.d		d	755	0	0	-	-	-	-	-
 /etc/network/if-post-down.d		d	755	0	0	-	-	-	-	-
 # uncomment this to allow starting x as non-root
 #/usr/X11R6/bin/Xfbdev		     	f	4755	0	0	-	-	-	-	-