ARM: exynos_defconfig: Set recommended options for systemd
Set following options to a value recommended by systemd (which also
matches the multi_v7 deconfig):
1. Enable AUTOFS4_FS - for systemd.automount [0];
2. Enable BLK_DEV_BSG - SG v4 for recend udev [0][1];
3. Disable UEVENT_HELPER_PATH - legacy hook for hotplug, forked for each
uevent, slows down booting [0];