android-tools-conf-configfs: read android device serial number

Read android serial number value from sysfs node
/sys/devices/soc0/serial_number instead of kernel command line.

Upstream boot managers e.g., systemd-boot does not populate
kernel command line with parameter androidboot.serialno.
This approach generalizes and makes serial number population
independent of bootloader that loads kernel.

Signed-off-by: Vishwas Udupa <quic_vudupa@quicinc.com>

dynamic-layers/openembedded-layer/recipes-devtools/android-tools/android-tools-conf-configfs/qcom/android-gadget-setup.machine

@@ -1,4 +1,4 @@
 manufacturer=Qualcomm
 model=`hostname`
-androidserial="$(sed -n -e '/androidboot.serialno/  s/.*androidboot.serialno=\([^ ]*\).*/\1/gp ' /proc/cmdline)"
+androidserial="$(printf "%x" "$(cat /sys/devices/soc0/serial_number)")"
 [ -n "$androidserial" ] && serial="$androidserial"