The find command to retrieve files from /etc/sysupgrade.conf and
/lib/upgrade/keep.d/* is used twice in almost the same way.
Move it into a function to consolidate, enhance readability and make
future adjustments easier.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Acked-by: Paul Spooren <mail@aparcar.org>
Reviewed-by: Philip Prindeville <philipp@redfish-solutions.com>
