[aboot]: Send serial number for USB enumeration

For eMMC targets, sending product serial number from CID of MMC as
serial number for USB enumeration to kernel as well as for fastboot.
For NAND targets, using target name as serial number.

Change-Id: I9cbf865ba8a7747ad89c7d12461b91d07a8d5403
CRs-Fixed: 276165
6 files changed