bbb: use RAUC eMMC layout

This, unfortunately, means that the system will no longer boot from the
SD card:

- U-Boot is set to store its env in the p1 VFAT partition
- rootfs' /boot is something else (kernel, etc) than what gets mounted
on system's /boot
- rootfs' /boot/boot.scr contains device numbers which refer to the eMMC
block device, not to the SD card

I think it might be possible to add some workarounds, such as exporting
the number of an "active MMC device" to an U-Boot variable or something,
but hey, let's give up. The only thing that I need is *some* method of
flashing content to the device, and any distro is good enough for that.

Kill services which are no longer useful, such as Avahi (originally used
for MDNS), and the tty-over-USB which only holds up the build.

Also sync the config with clearfog.

Change-Id: Ia966448a05ed5ce52747f5e7169136232f5502c2
diff --git a/board/czechlight/beaglebone/uboot.fragment b/board/czechlight/beaglebone/uboot.fragment
index d231b5d..62c796c 100644
--- a/board/czechlight/beaglebone/uboot.fragment
+++ b/board/czechlight/beaglebone/uboot.fragment
@@ -1 +1,3 @@
 CONFIG_CMD_SETEXPR=y
+CONFIG_ENV_FAT_DEVICE_AND_PART="1:1"
+CONFIG_BOOTCOMMAND="fatload mmc 1:1 ${scriptaddr} /rauc.scr || reset; source ${scriptaddr} || reset"