buildroot: arm: Update BR2_ROOTFS_OVERLAY

This was done as part of #101 but the change was never made back in the
config.

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Author: nathanchance

buildroot/arm.config

@@ -5,7 +5,7 @@ BR2_BINUTILS_VERSION_2_31_X=y
 BR2_GCC_VERSION_8_X=y
 BR2_TARGET_GENERIC_ROOT_PASSWD="root"
 BR2_TARGET_GENERIC_GETTY_PORT="ttyAMA0"
-BR2_ROOTFS_OVERLAY="../overlay-poweroff"
+BR2_ROOTFS_OVERLAY="../overlay-reboot"
 BR2_PACKAGE_BUSYBOX_SHOW_OTHERS=y
 BR2_PACKAGE_BASH=y
 BR2_TARGET_ROOTFS_CPIO=y