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 fixes some validation, makes variable declarations local,
removes unnecessary curly brackets.

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

Signed-off-by: Nuno Goncalves <nunojpg@gmail.com>