init.qcom.usb.rc: Set serial string on init

Currently init.qcom.usb.sh is writing the serial number into
android sysfs entry. But during bootup, .rc file is writing
default composition before .sh gets executed. This results USB
driver sending default serial string to host due to port hopping
happens. Hence write ro.serialno to the sysfs entry on init once.

Also remove reading persist.usb.serialno which is required only for
NAND based devices as all future targets are emmc based devices.

CRs-Fixed: 659235
Change-Id: Iddb0875fe0aff9aa9d53850861cc54735e5006d7
Merge "init.qcom.usb.rc: Set serial string on init"
Sign recovery image

LK now requires recovery image to be signed. This
is a new change to ensure that only signed images
are used.

Change-Id: I25fef9c311370e3f26d2d09b577575cd2a16f880
Merge "Sign recovery image"
common: add support to sign boot image

adding rules for generating signed boot image

Change-Id: I53710c2b4b8e8750c29d9c46c51a3e4ff0f270d2
Merge "common: add support to sign boot image"