scripts: add CAMEO tag generator

scripts: add CAMEO tag generator

This script inserts CAMEO tags into an uImage to make U-Boot
of DGS-1210 switches happy.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Suggested-by: Sander Vanheule <sander@svanheule.net> # Mutual checksum algorithm
[commit title prefix, trailing whitespace, OpenWrt capitalisation, move
CRC calculation comment, use UIMAGE_NAME_*, remove parentheses for
return, use f-string instead of str()]
Signed-off-by: Sander Vanheule <sander@svanheule.net>
(cherry picked from commit f9e840b65700e1cdff6d066d39c163bac936d046)