nft-qos: Update init script

nft-qos: Update init script

This replaces the use of uci_validate_section() with
uci_load_validate(), which removes the need to declare local variables
for every config option.

This also adds a validate section to service_triggers(), and fixes some
variable name typos in qosdef_init_static().

Signed-off-by: Jeffery To <jeffery.to@gmail.com>