Deprecate -u flag in flash.sh

- Now that u-boot support flashing and erasing the same targets as LK,
we don't need to do any special casing during flashing. Whatever
fastboot implementation is active when the flash process starts will be
used the entire time.
- Keep the -u flag in our getopts, but don't set anything with it.

Change-Id: I322f363bbf50d43bad23efeb2a3c68fb9fdc1ba2
1 file changed