gpio: davinci: Fix the number of controllers allocated

Driver only needs to allocate for [ngpio / 32] controllers,
as each controller handles 32 gpios. But the current driver
allocates for ngpio of which the extra allocated are unused.
Fix it be registering only the required number of controllers.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>