firmware-utils: tplink-safeloader: use revision field

firmware-utils: tplink-safeloader: use revision field

The structured soft-version partition has a field which contains a
(source) revision number. Factory images used to include this, but
it was accidentaly removed during an earlier refactoring.

Include the source revision number again in the generated soft-version
partition. Additionaly, also show this revision number when printing
image info.

Fixes: 1a211af2cb3b ("firmware-utils: tplink-safeloader: refactor meta-partition generation")
Signed-off-by: Sander Vanheule <sander@svanheule.net>