busybox: update bbappend to 1.22.1

Signed-off-by: Anders Darander <anders@chargestorm.se>
linux-yocto: build zImage for Beaglebone

We prefer to be using zImage, as that's the upstream default (at
least using newer U-Boot versions).

Signed-off-by: Anders Darander <anders@chargestorm.se>