scripts/diffconfig.sh: fix output if TARGET_PER_DEVICE_ROOTFS is set

diffconfig show packages selected as dependencies of
TARGET_PER_DEVICE_ROOTFS as individual selected.

Signed-off-by: Mathias Kresin <dev@kresin.me>

scripts/diffconfig.sh

@@ -7,6 +7,7 @@ grep '^CONFIG_ALL_NONSHARED=y' .config >> tmp/.diffconfig.head
 grep '^CONFIG_DEVEL=y' .config >> tmp/.diffconfig.head
 grep '^CONFIG_TOOLCHAINOPTS=y' .config >> tmp/.diffconfig.head
 grep '^CONFIG_BUSYBOX_CUSTOM=y' .config >> tmp/.diffconfig.head
+grep '^CONFIG_TARGET_PER_DEVICE_ROOTFS=y' .config >> tmp/.diffconfig.head
 ./scripts/config/conf --defconfig=tmp/.diffconfig.head -w tmp/.diffconfig.stage1 Config.in >/dev/null
 ./scripts/kconfig.pl '>+' tmp/.diffconfig.stage1 .config >> tmp/.diffconfig.head
 ./scripts/config/conf --defconfig=tmp/.diffconfig.head -w tmp/.diffconfig.stage2 Config.in >/dev/null