Una forma sencilla de sacar eso es:
Código:
(SELECT country, COUNT(provider_id)AS total
FROM provider where country in ('Espana', 'Argentina', 'England', 'Ecuador', 'Germany') GROUP by country ORDER BY total DESC Limit 5)
UNION
(SELECT 'otros' AS country, COUNT(provider_id) AS total FROM provider where not country in ('Espana', 'Argentina', 'England', 'Ecuador', 'Germany'))
Otra forma ya sería empleando un if/case en la select.
Un saludo.