meta-android: android-system: add additional boot marker

We're adding our own bootmarker now to know when the android system is fully booted and
it's safe to proceed with the outer system startup.

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-android: android-system: correct script to disable several android services

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-android: kernel_android: rework boot partition discovery

Signed-off-by: Simon Busch <morphis@gravedo.de>