Rewrite flash script to behave like Enterprise

- Rewrite this like a real program, lots of things cribbed from the
Enterprise script.
- Add serial number parameter
- Allow specifying path of files, otherwise use PRODUCT_OUT, and finally
fall back to the script's directory.
- Leave in a flag to allow just booting LK (-l)

Change-Id: I26c997b345da00fc5efedb07c450c5d4fecb6c3b
1 file changed