qmi: sort config variables a little and fix minor bugs

qmi: sort config variables a little and fix minor bugs

Group 'local' declarations and 'json_get_vars', sort alphabetically within groups, and split off more generic parameters.

- delegate and sourcefilter were not declared as local variables

Signed-off-by: Leon M. Busch-George <leon@georgemail.eu>
(cherry picked from commit bf768867dc0eea6b51d2db90a8f1380cc52529c1)
Signed-off-by: Felix Baumann <felix.bau@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/18965
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>